"What are you doing, brother?"

He dropped his hands to his sides and stopped moving. His sister had caught him masturbating in bed!

"Brother? I heard you."

He didn't move. Why, oh why, did they have to share a room? Yes, it had a curtain running down the middle for privacy, but now that he was sixteen and her fifteen, they should have separate rooms! He knew why, though; his father was the only one who earned a salary, their mother staying home to school them, so they could only afford this two bedroom apartment. He thought that maybe they were holding out with just two bedrooms for a couple more years until he went off to college or the military, or whatever, but he was a teenage boy! He had to relieve the pressure of his hormones in private.

"Hmp."

He waited until his sister's breathing became regular before he started again. Now that the Coronavirus lockdown was in its tenth month, he had no real inspiration to whack off to, other than women on TV or online. He struggled to remember a video from a pornographic site he had managed to reach a couple weeks ago that hadn't yet been blocked by his parents' "nanny" software; it had been unreachable the next day. His slim cock hardened again as he thought about the busty blonde stepsister in the video, spying on her stepbrother masturbating in the shower as she pleasured herself, and after she was caught...

"Aha!"

A flashlight shone on him as his sister slipped around the curtain. There would be no doubt what he had been doing, with his comforter tenting up and down repeatedly. "Shit! Sis..."

She turned off the flashlight and he felt her sit on his bed. "There's nothing wrong with it, bro. I do it too, y'know."

He did know. Sometimes after he orgasmed, he heard her gasping on the other side of the curtain. It made him feel weird when that happened, and he had to plug his ears so that he could go to sleep.

"Can I watch?"

His eyes widened. "Wa...watch? I...no! Go back to your bed, sis."

She shifted. "Pleeease? I'll let you watch me afterward."

He almost rebuked her, then, telling her in no uncertain terms that this was unacceptable, and to return to her own bed or he would tell their parents, when a familiar noise started up on the other side of his wall. A soft thumping, and a female voice, "Oh! Oh! Yes! Harder..." Their parents were having sex again.

His cock lurched. Muffled like that, the voice could be any woman being pleasured.

"Mmn..." He felt his sister shift position on his bed again. He felt something bump his penis through the covers.

"Hey!" he hissed at her.

"Oh, sorry," she replied, and her extremity retreated.

He reached up and turned his side table lamp on. A light the intensity of the sun blinded him, and he blinked until it faded to the normal 40 watts of illumination. He saw that his sister was sitting spread-legged near the foot of his twin sized bed. When she had done that, her foot must have extended between his legs and brushed his crotch. She was wearing a long t-shirt, but her current position had bunched it up around her hips. Her hands were between her legs, keeping the front of the t-shirt pulled down, and her face was flushed.

He considered his sister. Not busty like the blonde from the pornographic video, and not even a blonde, with her brown hair, so much like his and their father's. She was pretty, though, and showing off some nice, slim legs...

He shook his head. His penis wasn't getting soft, which meant that it was holding some of the blood that would otherwise have helped his brain to think straight. "Why do you want to watch me?"

She nibbled her lower lip, her eyes down. "We both masturbate, and we hide it from each other. Wouldn't it be better if we didn't have to hide?" She locked her eyes to his, and he was transfixed by the intensity of her gaze. He had never seen this look on her face before. His penis twitched again.

The muffled moans continued, "Ohh...from behind...yessss..." Thump thump thump...

"Okay."

His sister's eyes widened in delight. "Yes!" she exclaimed softly and waited.

He took a breath and then pushed his covers off. He was naked from the waist down, having lowered his boxers before he started. He heard his sister's breath catch at the sight of his hard penis.

"Wow..." she breathed.

He felt a little chuffed at that. She was the first person to see his penis since he had hit puberty, and he didn't know if his erection was normal or small. Pornography, even the little he had seen, certainly didn't provide a standard set for comparison. He grasped his member and started to stroke.

His sister kept her eyes fastened on it, her mouth slightly open as he pleasured himself. He didn't want to keep watching his sister as he masturbated, so he lay back, closed his eyes, and replayed that pornographic video in his mind's eye.

In it, the busty blonde pushed the door of the bathroom open and saw the slim, athletic form of her stepbrother through the foggy glass of the shower door as he masturbated. She unzipped her tight cut-offs and shoved her hand inside in order to pleasure herself as she watched.

He wondered what a real vagina felt like. The blonde's looked amazing later in the video.

"Unhh!"

"Oh! Yes! Yes!"

Upon hearing his father grunt through the wall as he filled their mother's vagina with his semen, and her crying out in pleasure in response, the brother started to orgasm himself. He grunted as silently as possible as his cum shot high in the air and splashed down upon his chest. Finally, he squoze the last drops from his shaft and relaxed.

"That...was...amazing!"

He opened his eyes. He had almost forgotten that his sister was watching! He suddenly felt very self conscious, and went to pull up the covers.

"Don't you have to clean that up?"

Yes, of course he did. He let go and reached for the tissue box on his side table. His sister continued to watch, wide-eyed, as he sopped up the silky white mess. Finally, he tossed the sodden tissues into his waste basket, pulled up his covers, and lay back, finally relaxed and ready for sleep.

"Okay, my turn."

He looked back down at his sister as she reached between her legs. Was she really going to...?

One hand slipped under her t-shirt while the other continued to hold it down, hiding her vagina from his sight. Her hard nipples poked through her shirt. She moaned as she touched herself and closed her own eyes.

"That's not fair."

She opened her eyes and looked at her brother, who had sat back up to regard her. "Not fair?" she asked.

"You saw my penis," he explained. "I should be able to see your vagina."

She considered for a moment, and then, nodding, she pulled her t-shirt up enough so that he could see between her legs.

He noted some light brown hair surrounding a puffy, vertical slit. He narrowed his eyes. This wasn't like the woman's in the pornographic video, whose vaginal lips had been spread open, showing a pink entrance that looked wide enough to accommodate her "stepbrother's" penis. His sister's seemed closed-off, unwelcoming.

Her face red with embarrassment, she moved one finger to the prominent little bud near the top of that slit and rubbed it. She moved her other hand up to her hard nipples to caress and tweak them through her t-shirt.

She closed her eyes as she thought about what her brother had just done, his hand sliding up and down his beautiful hard penis. His face had been screwed up in concentration, and then as he reached his release, his features had softened, transforming into a beatific configuration she had never seen before as he released his essence.

"Oh! Oh!" she cried out as she came quickly to the memory. Her slim teenage body shook as pleasure blossomed from her clitoris, the feeling somehow amplifying, connected to her hard nipples and as she tweaked and rubbed them.

"Wow!"

She looked up at her brother watching her. Suddenly embarrassed, she pulled her t-shirt back down to cover her vagina.

"Um..." he said.

"Yeah..." she replied.

"I'm hard again." Her brother pulled his covers off to punctuate his statement.

"Oh."

Bang bang! "Go to sleep, you two!" That had been their father on the other side of the wall.

His sister dashed back to her bed as he reached over to turn the lamp off.

"G'nite sis."

"G'nite bro."

---

He thought that what they had done the previous night would change their relationship, but on the next day everything was normal. It was a weekend, so she stayed in the bedroom doing online things with old church friends that she hadn't seen in person in months while he played video games in the living room. When they were called to lunch they ate their grilled cheese sandwiches and tomato soup without any weird looks between them.

That evening, they watched TV and movies with their parents, just like they usually did, and then they went to bed.

After they lay there a bit, she whispered out, "You wanna do it again?"

He really did. Not having to hide it from each other was a wonderful thing. "Yeah...I'll come over there so we're farther from Mom and Dad's room."

"Good idea."

He rose and went over to her bed while she turned her bedside lamp on. Like his, her bed was a twin size so there wasn't a lot of room; he sat below her legs. "I was thinking," he said, "if I go first and then you, I'll get hard again, and then we'll never get to sleep. So, how about you go first and then me?"

She was pleased that her masturbating excited him enough to get hard again, but she had another idea. "How about we both do it at the same time?" Then she pushed her covers aside and pulled her t-shirt up to reveal her cute little vagina.

"Oh...yeah," He pulled his boxers off, revealing his very hard and ready erection.

She spread her legs and reached down to play with her pleasure button, but couldn't get a very good look at his penis while he was sitting sideways with his feet on the floor. "I can't see...can you turn toward me?"

He sat further up onto the bed and turned to her, but then he couldn't see her vagina very well. He got up onto his knees and moved forward, between her legs.

"Yeahhh..." she moaned as she lay her head back onto her pillow. She had a very good view of him sliding his hand up and down his hard penis as it was pointing at her. Yes, she thought, this felt right.

He had originally meant to just think about the pornographic video again, but there was a real, live vagina, right there in front of him! As long as he didn't look at his sister's face, he could pretend it was any woman's. His hand skimmed faster along his erection.

She was using her other hand to rub her nipples through her shirt, gasping as she watched him masturbate.

"Um...do you think you could pull your shirt up all the way?" he asked. He hoped he wasn't pushing this too far.

Apparently he wasn't, as she rose to her elbows and pulled her shirt right off. "You too," she commanded, and then, very quickly, they were both naked.

He watched as she returned to rubbing and tweaking her nipples, no longer limited by her shirt. These were the first real breasts he had ever seen, small compared to the women in porn, but beautiful. He had seen them pushing her shirts out, with and without a bra, but seeing them like this was amazing.

He realized that he was already getting close. He also realized that he had no idea where to spurt. He was between his sister's legs, and he didn't want to lose his orgasmic momentum. She had closed her eyes and was breathing heavily, her finger moving fast on her clit.

He grunted and loosed his sperm, pointing his penis right at her clitoris.

She heard him grunt and then felt hot liquid splash on her clitoris, hand, and all around her vagina. She had been so close to her own orgasm that this didn't just push her over the edge, it shot her past it like a rocket ship!

"OhhhHHHH!" she cried out softly, orgasming hard, her hips instinctively rising off of the bed as her fingers rubbed furiously at her clitoris. With this new angle, the next splash of his semen hit directly on the tight split between her vaginal lips. The feeling of another dollop of hot cum hitting her privates sent her into a second orgasmic wave. "Uhh...uhh...uhh..." she moaned, her slim body shaking, overwhelmed with pleasure at this novel, forbidden sensation.

"Ohh wow..." he gasped as he fell back on his heels, utterly spent. That had been a strong one!

Finally, she came down from the most powerful orgasm of her young life and relaxed, her legs splayed, a silly grin on her face.

"Shit..." her brother said as he went to grab the box of tissues from her side table. "I'm sorry, sis! I didn't know where to shoot." He held out the box.

"It's fiiinne..." she breathed as she grabbed a couple of tissues and started to dab up the mess. She cleaned up the white gobs on her pubes and perineum, and what had dripped under her butt, but with her angle of view she didn't notice the pearlescent liquid shining between her vaginal lips. She pulled her covers up while her brother went back to his bed.

"G'nite bro."

"G'nite sis."

For the rest of the night, her brother's sperm did their best to slip between her vaginal lips. The few that succeeded began their preprogrammed way deeper inside the virginal teen girl.

---

His sister had resolved not to let what they were doing mess up their relationship. They had been close growing up, only a year apart in age and their own best friends, though once her brother had become a teenager, their relationship had changed and he started treating her more like an annoying kid. In the last year or so, though, they had started to get along again as she likewise became more mature.

She, however, was not technical-minded, and therefore did not have the same access to inspirational online media that he did when masturbating. While he had found the occasional unblocked pornographic video on his tablet, she only had music videos, TV, and movies, and none of those were remotely sexual thanks to the efforts of her conservative parents. When she awoke one night to hear her brother masturbating, she had been excited in a way like never before, and her first orgasm, a little after he had finished and fallen asleep, opened her eyes to a new source of excitement.

On Sunday, they virtually attended church via streaming video. It just wasn't the same thanks to the pandemic, but privately the kids agreed that it was nicer to not have to dress up and say hello to a bunch of people they didn't really know. They barely went out prior to the lockdown, since their mother homeschooled them, so it was just one more place they didn't go, and they didn't miss it.

That night began much as the previous, with her brother kneeling between her legs as they masturbated. As she got herself close to orgasm, though, her brother touched the tip of his penis to her vaginal lips as he stroked himself. Her eyes flew open. "No! We can't have sex!" she hissed.

He pulled back and she kept her eyes on him until he came, blasting her clit and vagina with his sperm again and giving her another massive orgasm at the sensation of his hot semen splashing onto her privates. She fell asleep, again unaware that a tiny amount of her brother's sperm was making its way deeper inside her.

---

Their mother got them up bright and early for their lessons. The woman had been a teacher before marrying their father, but once the kids were born she had naturally stayed home with them while he continued to work. Once his son got old enough to go to school, the man insisted that his wife homeschool the boy, and then a year later, the girl.

One thing that was never taught to the kids was sex education, so they had no idea how babies were made. When they had asked, their mother talked about marriage and love. The kids naturally thought that you couldn't get pregnant, however that happened, without getting married first.

That night, the sister asked, "What if I masturbate you, and you me?" That way, she figured, she'd make sure that her brother didn't try to have sex with her. She had to save herself for marriage!

Her brother was all for it, and he got right up between her legs, his penis over her stomach, as she lay back on her bed. She took his erection in her hand, marveling at the feel of the hard shaft underneath the strangely shifty skin before she started to stroke.

"That feels really good, sis," her brother whispered as he reached down to touch her vagina. He was a bit awkward at first, but she directed his fingers to her clitoris and then lay back again, getting used to stroking his cock as she felt the pleasure he was giving her flowering between her legs.

One of his fingers tried to slip between her vaginal lips but she reached down and grabbed his hand. "No penetration," she stated. That was too much like sex, and that was a firm line for her.

Soon her brother was rubbing her clitoris just right, and he also reached up to palm one of her breasts. It felt amazing when someone else did it! She figured it was like trying to tickle yourself; you just can't. Alone, she would never be able to make herself feel like she currently felt with her brother's hands on her.

She was getting close. It was going to be a big one!

"I'm gonna shoot, sis," her brother warned.

She pushed him back a little as she stroked so that the tip of his cock was aiming right at her vagina and closed her eyes. Almost, almost...

As her stroking pushed him over the edge, he thrust his hips forward a little so that the tip of his penis touched where her vaginal lips came together just below her clitoris. She had no chance to correct the position as his first blast of dangerous, sperm-laded semen shot into the small gap.

"Unhh!" she cried out as she felt the hot pressure of that spurt ricochet off the top of the entrance to her vagina. Her orgasm crashed down upon her like a tidal wave, and she arched her hips while continuing to stroke her brother's cock, causing the tip of it to slide down, along her slit. This lined it up with her vaginal entrance proper, and his next spurt shot between her lips and spattered her hymen, the result being some of her brother's seed slipping through that porous barrier. She felt a spreading warmth inside her, where nothing had ever touched before, and this new sensation redoubled her orgasm. "Oh-hhhh!"

After his initial spurts, her brother realized that he was going to upset his sister by not following her instructions, so he backed off and shot the rest of his cum onto her clitoris and vaginal lips.

Then they heard the door to their parents' bedroom slam open. He barely had time to pull up his sister's covers and dive under his own before their father rushed into their bedroom, clad only in boxers.

"What's going on in here?!" their father yelled.

"I think she was having a nightmare, Dad," the brother responded.

Their father went to her bed and sat, touching her face. "You okay, sweetie?" he asked, calm now.

She was still shaking from her orgasm, which fortunately for them made it look like it was from a scary dream. "Yes, Daddy."

"Do you want to come sleep with your mom and me, like old times?"

Her brother's eyes widened in fear. That would not turn out well!

"No, Daddy," she responded, "I'll be fine."

He kissed her forehead. "Okay, sweetie, sleep well." Then he clicked off her lamp and returned to his bed.

"G'nite sis."

"G'nite brooo..."

And then she was asleep. Not having had a chance to clean up her brother's sperm, the remainder on her vaginal lips soaked in all night while the ones that he had shot inside her unprotected vagina did their best to impregnate the naive teen.

---

The next night...

"We can't, brother. We're gonna wake Dad up again. Just do it yourself, okay, and I'll do the same over here?"

They did, and it was hot, hearing each other gasping and moaning, but nothing like when they did it together.

---

Saturday rolled around. The siblings had masturbated separately all week and, while they had reached their release every night, they were getting antsy, missing the super orgasms they had together.

Their parents had booked a bed & breakfast weekend for themselves before the pandemic had started. Luckily, it was one of those ones where they had a cabin to stay in, separate from other vacationers, so they could socially distance while enjoying their brief downtime.

"You're in charge, buddy," his dad said to him as he handed him a debit card. "Call me if there are any problems, okay? Or Grandma."

The brother nodded, and soon their parents were gone. He looked over at his sister, and found that she was looking back at him with undisguised lust. They wouldn't be waiting until nighttime. Their clothes flew everywhere when they got into their bedroom.

She lay back on her bed and stroked him while he again played with her clit. God, they had missed this, and they wouldn't have to keep quiet!

Again, he nosed the tip of his penis at the vertical gap between her vaginal lips.

"No, brother!" she admonished him and stopped moving her hand.

He sat back. "But it's like a kiss."

"A kis--? MMPH!"

He had leaned forward to press his lips against hers. As he did that, the tip of his penis bounced up, off of her clit, and got sandwiched between them, pressing against her stomach.

She felt an electric shock run through her. This was her first kiss, and with her brother! He continued to kiss her, the muscles of his mouth working to change the pressure and angle of it. She felt his tongue slip along her lips. Soon she was kissing him back.

He broke the kiss and moved back. "See? Just a kiss, and I didn't put my tongue into your mouth."

She lay there, confused. She wouldn't have minded him using his tongue...

"My penis was just kissing your vagina; no tongue. No penetration."

"Oh. Um, can you kiss me again?"

He pushed the tip of his penis against the entrance to her vagina again.

"No, I mean a real kiss, brother!"

He leaned down to kiss her again but didn't remove his penis from where it pressed. Soon she reached down between them and stroked his cock. He reached up to fondle her breasts while they continued their lip lock, but at this angle he was unable to play with her clit so she swiped the head of his cock along it, stimulating herself.

He broke the kiss. "Gonna shoot..." he moaned.

She moved her hand faster on his shaft while continuing to bounce it off of her clitoris. When he grunted and she felt his hot cum splash on her clit, she angled it down so that it nestled between her vaginal lips as he blew about half of his load of baby-making sperm between them. Her own orgasm exploded as she felt his warm stuff splash around the entrance of her vagina.

"Just a kiss," she agreed after she could breathe again.

She was surprised but happy to not have to clean up as much of his spermy mess from the outside of her vagina as usual. It made a mess of her panties as some of it dripped out later, though.

---

"Can we try something new?" he asked while they sat on the couch.

It had only been a couple of hours, but she knew what he meant. She got up to head to their bedroom, but he took her hand.

"Here," he said, directing her to get to her knees in front of him as he unfastened his jeans and pulled both them and his underwear down. His hard cock flopped out.

She was still in awe of it. Now she had a close-up view, and she took it into her hand.

After a few strokes he asked, "Will you suck it?"

She looked at it as if it was a snake. "But you pee from there!"

"I can't pee while it's hard...well, it's really difficult to, anyway." She looked at him dubiously. "I promise I won't! Pleeease?"

She tentatively touched her tongue to the tip (try saying that five times fast!) and gave it a lick. It didn't taste like pee, so she put her mouth over the head and gave it a little suck, making him gasp. She then moved her lips down his hard penis. Again, she marvelled at how yielding the skin was over such a firm shaft.

"That's amazing, sis..." he moaned as he watched her.

She grinned a little and moved her mouth up and down his shaft faster. She found that if she used her hand to stroke the lower half of his shaft while sucking on the top half, it worked really well.

"I'm gonna shoot, sis..."

She pulled her mouth off of him but kept stroking. She didn't want him to shoot in her mouth!

"Pleeeasse..."

She realized that they were about to make a huge mess otherwise, so she trapped the head of his cock in her mouth as he grunted. She felt his penis throb and then a warm splash of his stuff filled her mouth. She thought that it wasn't bad, but then he shot more, and then still more! "Mmff!" She gurgled, her mouth full. She couldn't breathe!

She sucked out the last of his cum, pulled off of him, and then swallowed reflexively. "Gluck!" She covered her mouth...she felt that she might barf! "Uhk..." She made a face as she swallowed the rest of it down. She stayed still for a minute, evaluating the condition of her stomach.

Finally, she stood and then lay back on the couch next to her brother. She pulled her jeans and panties down. "You do the same for me now," she demanded.

He had seen the stepbrother in that pornographic video lick his stepsister down there, so he had a good idea of what he needed to do. He moved between her legs and started to lick at her now prominent clitoris.

"Oh yeahhh..." she moaned, watching him, "Oh, brother..."

He licked there for a few minutes and then started to slide his tongue up her vaginal cleft, bottom to top, ending each with another flick at her clitoris.

"Ohh..." she moaned.

As his spit inundated her vaginal lips he saw them start to separate. He used his thumbs on either side of them to pull them further apart as he continued to lick, bottom up, flick, bottom up, flick. Soon he could see the pink flesh of her vagina through the widened opening. On his next lick, his sister's body tensed up and shook as she came. "O-hh! Bro! Ohh!" Her vagina suddenly tasted slightly acidic.

He was hard again. As his sister recovered from her orgasm, he moved between her legs and started to stroke his cock, bouncing the tip off of her clitoris as he did so.

She hissed, as her pleasure bud was overstimulated, and reached down to move his member lower, but with her now open vaginal lips, instead of pressing against those, the head of his penis was now between them.

He pulled back, not wanting to penetrate his sister, but continued to stroke. As he beheld her moist, pink folds, he realized...

"I'm gonna shoot, sis. Shit, we're gonna make a mess of the couch!"

She grabbed his penis and slotted the head between her vaginal lips. "Nope! Kiss me..."

He leaned forward and pressed his lips to hers, the change of position pushing the head of his penis a little into her virginal channel. Feeling the incredible heat of her vagina pushed him over the edge. "Unnmm!" he moaned into her mouth as he blasted her now raggedy maidenhead with spurt after spurt of dangerous incestuous seed.

Feeling all of her brother's warm stuff shooting into her as his hard penis throbbed in her hand, she came again. "Mmm! Uhhmmhh..."

---

They ordered pizza for dinner and watched a movie, but they quickly got bored of it. It was getting late so they decided to spend some quality time in bed, his this time, since they didn't have to be quiet.

Her brother lay back as she climbed astride him, facing each other. She figured out that she could rub her vaginal lips along his hard shaft, back and forth, and that felt good for both of them. It also had the effect of splitting her labia and opening up the mouth of her vagina, much like when he had licked her earlier, so when he announced that he was going to shoot, and she angled the head of his cock between her vaginal lips, the entrance to her reproductive system once again swallowed it. As she manipulated her clit and cried out in her own orgasm, her brother grunted and filled her up with another hot batch of baby-making sperm.

---

He woke to find he was sleeping in the "big spoon" position, his sister's cute little bum pressed up against his stomach. Breathing in her scent, he felt his penis getting hard again. He reached around and palmed one of her beautiful breasts, rubbing the nipple until it got hard. Then he moved his hand down between her legs, but they were closed.

He thought for a moment and then moved his hand around her hip and further down, below her bum. Pushing her legs up and away from him, he was able to reach her clitoris from behind.

"Mmm..." she moaned as he played with it. When he felt that she was wet enough, he replaced his hand with his hard penis. "Sis?" he whispered. There was no answer; just her heavy breathing. She was still asleep!

He was just going to masturbate with the tip of his penis between her vaginal lips, but then he wondered. She was notoriously difficult to wake once she had fallen asleep. Just how far could he go?

He shifted downward in order to get the angle right, and thrust. He was rewarded by his new favorite feeling of his sister's hot vagina swallowing the head of his penis. She moaned in her sleep again.

He pushed a little harder but wasn't able to make any headway. He pulled back a bit and adjusted the angle. This time when he pushed he felt another inch of his hard penis enter his sister's body, and she groaned. He couldn't tell if that was pleasure or discomfort, so he paused. After an excruciating minute, his penis throbbing with need the whole time, he pulled back and then pushed forward again. Again, she groaned or moaned and one more inch went inside. Again, he paused.

Then he felt her roll her hips, and her vagina squeezed his member. She was into it! He pulled back a little and thrust again slowly. This time he was sure she was moaning in pleasure. Was she awake? "Sis?"

Still no answer. Her sleeping body was reacting to his sexual invasion.

Invasion. He stopped moving. This was wrong. His sister had asked him not to penetrate her, and here he was, doing just that while she was sleeping! What a horrible brother he was! He carefully withdrew and went to the bathroom to take care of his throbbing erection.

When he turned on the bathroom light, he gasped. His penis had blood on it! He had hurt his sister! His manhood quickly deflated. He peed, cleaned the blood off, and returned to his bed. Whatever his sister did to him in the morning, he would deserve it.

---

When his sister woke in the morning, she felt sore between her legs. When she went to go pee, she saw blood and naturally thought that her period had started. What terrible timing! Her brother wouldn't want to deal with her flow, and they were only halfway into their weekend alone! She put a pad in her underwear and then went to help her brother with breakfast.

He was still feeling guilty, so didn't initiate anything, and she didn't either due to her period. However, she didn't understand why he was being so distant.

"Is everything okay?" she asked him as they watched TV.

"Um..." She didn't seem to know what he had done to her last night, but he still felt guilty. "Yeah, I guess. Are you okay?"

"Yes...my period arrived, though. I think I may have left some blood on your sheets. Sorry, brother."

"Oh!" He hadn't hurt her after all! Relief washed over him. "Um...so what does that mean, your period arrived?"

"It means that we can't have fun unless you like blood. I can still make you feel good, though." Then she thought for a moment. "Hmm...I have an idea...come with me!" She took his hand and he followed her into the bathroom. She took her clothes off. "Come on," she said, urging him to do likewise.

She examined the pad as she removed her underwear. "Just a few drops...maybe I'm just spotting?" Her period was notoriously random, sometimes late, sometimes heavy, sometimes barely anything, like this.

Her brother just shrugged his shoulders as he removed the last of his clothes. He was out of his depth in regard to the female cycle.

She started the shower and they climbed in. His penis had already hardened at the sight of her naked teenage body, and she took it in hand as the warm water cascaded over them. She rubbed the tip along her clitoris and up and down her vaginal lips as she stroked him, and since both of his hands were free, he took hold of both of her breasts.

"Careful, they're a bit sensitive," she advised him as she winced. Her breasts sometimes got that way when her period was coming. They also got that way when she was ovulating, but with her inconsistent fertility cycle, she didn't realize which was actually occurring at that moment.

"Kiss me," she directed her brother, and he did as she stroked the tip of his cock up and down her vaginal lips. But with her body careening into its first fertile time since she had become sexually active, it wanted more.

"Hold me." She put her arms around his shoulders and hopped up, wrapping her legs around his waist. He quickly moved his hands under her buttcheeks and pushed her up against the wall of the shower in order to keep her aloft. In this position, her breasts pressed against his chest, but not painfully, and she was still able to stroke his penis as it rubbed against her wet folds. Her body was thrumming with fertility hormones; she needed more.

"Use...tongue..." she gasped between kisses.

He pushed his tongue into her mouth and she moaned. Then she wrapped her legs tight around his waist, trapping the head of his penis in the entrance of her very wet vagina.

She broke the kiss. "Use tongue...down there...in me...ohhh..."

He realized what she meant. He let gravity take over, and her vagina slowly slid down his hard cock. They gasped at the feeling, her of being filled by her brother's hard member, and him at his sister's tight, wet fertility surrounding it.

Soon he was fully embedded inside her. "God, sis..."

"Do it...God, do it..."

He began to thrust. It was sore for her, but not as bad as she had thought it would be for her first time. As he buried himself in her, her clit was stimulated and she became even more wet inside. Soon he was thrusting into her harder and faster. She could feel her orgasm building, and knew it would be a big one.

He didn't know how he held out as long as he did, but his legs were starting to give out. As his tongue found hers again he grunted and thrust as deep as possible.

Her eyes flew open as she felt a warm, liquid fluttery sensation deep within her as her brother's seed splashed against her cervix. He hadn't cum during the night after deflowering her while she slept, and his testicles were very full. Spurt after spurt of her brother's potent teenage sperm hosed the entrance to her womb, and as her own orgasm blasted through her ripe body, her cervix spasmed open and closed, sucking much of that incestuous seed into her defenseless uterus.

---

Once they had crossed that line, there was no stopping the rutting siblings. They fucked almost constantly until their parents returned, and then her brother would make sure to cover her mouth with his own when she orgasmed at night, so as to not clue their parents in to what they were doing.

Her period was undependable, and she thought it had started the night before her first intercourse with her brother, so when it didn't arrive when it was really supposed to two weeks after that, she didn't know anything was wrong. But then it didn't arrive two weeks after that. Nor the month after. And she started to gain weight.

By the time her parents called her out on her obviously pregnant belly, three months later, it was far too late for an abortion, not that her conservative mom and dad would have considered that. She protected her brother, saying that it was a boy she had met online and that it had only happened once. Her parents almost threw her out, but then her brother spoke up for her, putting his foot down. If she was going, then he would as well.

In the end, their mother finally explained how babies were really made and the siblings realized their mistake. It didn't stop them from continuing to fuck every night, though...his sister got so horny when she was pregnant, and he found her gravid body, with its growing breasts and rounded belly, to be very sexy.

Once she gave birth, though, what were they going to do?

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