"Mom, Uncle Mark is here!" Sophie squeeled as she leapt up into your arms. You barely managed to get your hands up in time to catch her.

"How's my favorite little niece?!" You cooed at her, rubbing your nose on hers as she giggled in delight.

"I'm good, Uncle. I've been waiting for you to get here! You took forevvvvver." She groaned dramatically.

"I know, baby, but it's a long drive. I tried to get here as fast as I could, I know how long it's been. Okay, let me put you down so I can see how big you've gotten!" You set her down and looked her over.

Sophie had grown all right…. Right out of that cute little dress you and I had picked out for her for Christmas last year. It was the most beautiful shade of green, really highlighting her long red curls.

From the outside, your relationship had seemed really strange. I’m not gonna lie about that. Sophie was practically a grown woman now, she had friends, and did well in school. But.. when she was with Uncle Mark, she acted like a little girl again. She couldn’t help it.

It was like your relationship was frozen in time... but your bodies weren’t. You were in your 40s now, and Sophie was curvier every time we visited her. She was beginning to look less like a little girl, and more like a nymphette. But that didn’t change the fact that she wanted to cuddle and crawl all over uncle Mark. Something had to give… and this was the night it happened.

I watched as your eyes stuck on her thighs, the dress barely covering them. I elbowed you in the ribs, jarring you out of your staring.

"Sorry, honey," you apologized, "Okay, Sophie, let us in so we can see your mom too!"

As she turned to lead us in, her skirt fluttered up and we both got a peek of her teeny little panties. I heard your breath hitch.

"How adorable!" I breathed in your ear. I felt your back tense a bit, "It's okay, darling. Maybe after we put her to bed, you and I can have a little fun with them.”

You turned toward me and I could see how stiff your cock was. Your face was reddening, your breath coming too quickly.

You shook your head, trying to throw the thought of your little niece’s panties from your mind.

"Hey you two!" Your sister, Emily, said from down the hall, "Come in already!"

We made our way in and shut the door. I hoped the tent in your pants went down quickly enough to not be noticed.

Emily continued talking on, so I'd assumed it had. She went over where the emergency numbers were and where she'd be for the week.

Apparently the conference had come at the MOST inopportune time,

Her husband, Roger, was away on business too and Sophie wasn’t comfortable being home alone, so they found themselves in need of a housesitter.

"It's definitely not a big deal, Emily. I'm glad I had some time off work coming up anyway. I'd rather spend it here, with my best girl!" You winked at Sophie. She giggled and turned beet red.

Fuck. That blush. Like I said.. The fact that Sophie acted like a little girl around you was strange at first… but fuck did it make me wet. I couldn’t help it, either.

I squirmed a bit in my seat, grinding my soaking wet cunt a bit. I could *definitely* see why you loved this little game so much.

Something had changed in the last few years. When you came home from visiting Sophie, you would fuck me like an absolute animal.

I could tell that your thoughts about her had become… impure. Lustful. And you took it out on me and.. It was the best sex of my life.

Then we visited her together, and I must have made a good impression because she played this little game with me too.

Acting small, coy, a little bit of baby talk. Like she was a kid again. And words can’t describe how good our sex was that night. We broke the bed, remember baby?

And now we were here. Spending the night under the same roof as the sweet little Sophie.

I could already imagine the hot rounds of fucking that were going to happen tonight, after she went to bed. But...I could feel something in the air tonight.

Something had to give. Maybe it was because she had grown so much since Christmas. You could see her cute little budding breasts, her full ass that she had yet to fully grow into…

Maybe it was the fact that the three of us would be alone.

Ugh, I wished Emily would stop talking and just leave so I could grab my little vibrator from my suitcase and have some 'me' time in the bathroom,

but she wouldn't stop, wouldn't even take a breath to slow down.

I distracted myself by fantasizing how tonight was going to whisper naughty little things about Sophie as I jerked your cock later tonight.

Telling you to think about the fact that she was just a few rooms away.

Finally, Emily seemed to run out of steam as she checked her watch and realized she was going to be late.

She went to the door, picking up her suitcase. With a kiss to Sophie's head, a "be good for your Uncle" thrown over her shoulder, she was gone.

And it was just the three of us. Alone. The tension in the air was SO thick.. Right away I started thinking of ways to orchestrate something naughty, but sweet little Sophie beat me to it.

“Uncle Mark, can I sit on your lap while we watch some TV?” You glanced at me, and I could see the lust that you were feeling.

All three of us knew, right in this moment, that if you said yes, that something would happen. Something naughty. Something forbidden.

I smiled at you, and you made your decision. “Sure baby.” you said, patting on your lap. Sophie grabbed the remote and picked out some cute little cartoon.

I could see her eyes as she made her choice… and she wasn’t picking out something to watch… she was choosing what would be on in the background when she finally got what she wanted from Uncle Mark.

She blushed as she approached you, looking right into your eyes at first, but becoming bashful and turning away.

She kept her skirt down at first when she sat her little body down on your lap. Of course you were hard.

You were hard since the moment you first saw her at the door. Of course she felt it, but you both pretend that she couldn’t.

It made it so much hotter that you were both pretending you didn’t know *exactly* what was happening.

I sat on a chair on the other side of the room, not even facing the cartoon. I abandoned all pretense of watching TV.

I was watching two people in love finally taking the leap into becoming lovers. You both ignored me, and that was okay. This wasn’t about me.

Tonight had been in the making long before I was ever in the picture.

Sophie made the *cutest* little gasp when the hard lump in your jeans found its space against her sex through her skirt.

Just a few centimeters of fabric separated you from each other as she began gently rocking her soft hips, grinding your hard cock against your underwear.

Your eyes were unfocused * giggles* I swear.. I thought a line of drool was going to run down the side of your mouth. You’d *dreamed* of this day… for YEARS.

After a few minutes of you both gently moaning and gasping from rubbing against each others through your clothes, without so much as saying a word,

little Sophie reached back and pulled up her skirt, removing one layer of clothing separating you from her.

She started rocking her hips faster, building up a little rhythm. I was grinding myself into my chair trying to rock my hips in time with her. She was making me consider picking up my phone and sending a naughty message to my own uncle. You two were *such* an inspiration.

You were both gasping and groaning now. I just *knew* your cock was absolutely *dripping* with precum underneath your clothes. Your hands were on her thighs now, guiding her body to make you feel as good as possible. Your breathing was becoming ragged, getting closer and closer. But she beat you too it. I saw her breath catch and she held it. Her whole body shook as her sweet little body enjoyed its first orgasm with a man. She tried her best to hold her breath, only a few adorably squeaky little moans escaping.

As little Sophie shook through her orgasm, her hips stopped moving on your cock. You must have been *close* huh baby?

I thought so! Because what you did next certainly made it seem like you were.

Abandoning the innocent little game of pretend, you slipped your hand under her skirt and grabbed her by her ass, and moved her body yourself, using her little body to give you the friction you needed to finish.

Just a few seconds later, before her orgasm even subsided, you began to have yours. I’ve seen you cum *so* many times, but not like this.

Your whole body shook, and your face turned red as you filled your boxer shorts with cum. You almost looked ashamed as you made *such* a mess of yourself.

After you two caught your breath, Sophie stood up like nothing happened.

Trying to hide the afterglow of her little orgasm from her voice, and without looking she said “Uncle Mark… I think I’m going to go take a bath.”

It wasn’t until she reached the stairs to go up to the bathroom that she looked back at you, her glance heavy with lust.

She glanced at me, and I hope she saw the love that I felt for her in that moment. She winked, an invitation for us *both* to join her.