One day the next week I picked the girls up at the high school. I had brought a football and proposed walking over to the soccer field and tossing it around; Megan was dubious, but Cait said, with a twinkle in her eye, “Aw c’mon, babe, it’ll be fun. We’ll make it worth your while.”

The three of us played keep-away--tackle keep-away, that is. Even if she managed to catch the ball, Megan would panic when she saw Cait running at her:

“Your ass is mine, little chickie!”

“Eek! Yyeek!”

I loved watching Cait launch her meaty little body at Magan’s willowy frame, and seeing the gap between Megan’s thighs in her skinny jeans as she half-heartedly tried to escape. When Cait brought her down there would be much tickling and squealing, and sometimes grinding, so that I had to run over and break it up before somebody called the authorities.

When Megan was ‘it,’ Cait would throw the ball so high that Megan had time to run up and tackle me before it even got there. She would straddle me, shouting in triumph, her buoyant tits bouncing near my eyes, the buttons of her nipples showing through the fabric of her blouse. I would feel her silky ponytail falling in my face as she panted and her green eyes sparkled.

One time Cait came over to try and break us up, but I grabbed her ankle and we pounced on her; Megan tickled her under the arms and smothered her face with her boobs while I went for the soft underbelly until Cait managed to scissor my head between her powerful little thighs. Before I stood up, I had a look around to make sure nobody was close enough to be shocked by my erection.

Cait and Megan were not ready to be out—keep in mind, this was some years ago, and in small-town Michigan, far from the fleshpots of Ann Arbor. Cait especially cringed at the thought of wondering if each store clerk and classmate would be cool or get all judgy, or act cool but talk shit behind her back.

But with me as their beard, a beard with benefits, we could get away with a lot. When we went to an all-ages show, I could feel the envious looks of the guys as I walked in with the two of them, Megan in a black mini skirt and leather boots with a touch of goth makeup that suited her raven hair and pale skin, Cait in her usual outfit except for a sexy bra and tank top that showed off her luscious rounded breasts. As she danced, she liked to raise her hands high and slowly spin, offering herself to the room. Nobody had to know that both Megan and I were going to take her up on the offer.

Anyway, if people saw us out in our small town, they would think either that Megan and I were letting the kid sister tag along (how nice of us!) or that the cool girls were letting the dateless brother tag along. (I was fairly presentable, about six feet tall with brown hair and blue eyes, borderline skinny with wiry muscles from working rather than working out. But I had always been shy, terrified that any pretty girl I asked out would think, “Eew, really?” and turn away.)

Still, there were limits. When Cait went over to spend the night at Megan’s, I couldn’t exactly go along. I could, however, get the play-by-play from a bubbly, excited Caitlin the next day. I told her it must be an advantage to know what the other person is feeling because you have the same equipment.

“Yeah, it’s true that I can make just a little motion of the fingers send her over the edge. I love to watch her face, when she comes, how she gets so flushed, and then her lips get kind of soft and trembly.

“But I also like to drive deep into her pussy. It makes me wonder what it would be like to take a woman the way a man does, the way you and Megan fuck.”

This planted the seed of an idea that I would have to think about.

“And, um, uh, I wonder about the other way too, what it would be like to be the girl. But it would have to feel right, and would have to be someone I felt totally safe with.”

She glanced at me and then looked away, blushing fetchingly. Well, this was an idea I had been nursing for a long time, the dream of fucking my little sister. I smiled at her and pondered how I could make it happen. In the end, it didn’t require any scheming, just a little patience.

One night we were watching figure skating on TV (one of the nice things about having a bisexual sister is that you can compare notes about sexy girls), and as we cuddled there on the sofa, we talked about what we’d like to do to the statuesque American blonde (her favorite) or the waifish little Russian with melting dark eyes and a tiny ass (my fave). After a while, she moved over to sit on my lap, and as one of the skaters wriggled and spun, I started nibbling at her ear and fondling her breast, feeling her puffy nipple poke out under her shirt. With my other hand, I unbuttoned her jeans and felt her hard pubic bone, then pushed further down to her moist vulva and her little button. She moaned and started grinding back and forth onto my fingers, and within a few minutes, my hand was soaked.

She raised herself enough to slip her jeans and panties down as far as her knees, and I liberated my erection from my sweatpants. I pulled her back down and at first just pumped between her thighs and crotch, then pushed my head up to her slit, rubbing her labia with it until it was slick and she was frantic to have me inside her:

“Oh, oh, come on and fuck me, dude! I need to feel you in me.”

And then there I was, living my fantasy, fucking my dear innocent Caitlin. My head slid in easily, and as I thrust deeper and deeper into her body, I realized that Megan must have taken her hymen with her eager fingers; it was a strangely arousing thought. Feeling her sweet ass cheeks press into my hips,

I let my hands run greedily between her breasts and belly, tickling her navel. I felt so hard and engorged that I half expected to feel my cock-head pressing from inside, but that was silly.

I kissed and lightly bit her shoulder, making her squeal, then lowered my hand to massage her clit and feel my cock pumping into her. I whispered into her ear, “Oh fuck me baby sister, little Caitlin, you make me so hard! You are a dirty, dirty little girl!”

Whether it was my words or just the feel of my breath tickling her ear, this triggered her. I let her drive, and she bucked up and down at first, then let her whole weight bear down on me and ground urgently as if she were scratching an itch. She pressed my hand down on her crotch with her own small hand and gasped:

“Oh now fuck oh god oh fuck god that’s it that’s it!”

As I felt my own climax approaching, I wrapped my arms around her and hugged her to my chest, holding her breasts and then her heaving ribcage as if hanging on for dear life, squeezing my darling sister so tightly that I worried I might hurt her. But no, she was a sturdy little thing and kept encouraging me to fill her with my jizz, until all at once I shuddered and exploded, sending jets of semen deep into her hot young womb.

As my penis deflated inside her, Cait turned to sit sideways on my lap and we kissed deeply. I found myself tearing up with gratitude, and Caitlin asked if I was OK.

“Oh yes, thank you thank you Cait, you are so good to me. I am lucky to have such a generous sister, and such a fucking hot and horny one.”

Putting our clothes back in order, we noticed that we had made a little stain on the couch. When the ‘rents came home from their movie, we explained that we had had a bit of an accident with some nachos. They were busy arguing over whether Meg Ryan was too old to be a romantic lead, and didn’t seem to notice.