When I was 14, my uncle married a woman with 6 kids. The oldest girl was 13, and she and I hit it off from the time we met.
My parents had a couch in the basement where I would sit and play video games. It was place for me to get away from my siblings, especially since I had all sisters and they dominated the upstairs bedroom areas.
So my aunt and uncle came to visit one night and their oldest daughter came down to basement to see me. Everyone else was upstairs. I was laying on the couch when she came in, but I never moved so she could sit down. She sat right on me, right on my dick.
I don't know if she intended to sit on my dick, but she did. Obviously being 14 and always horny, my dick instantly started to get hard. She could obviously feel my dick growing under her butt, and looked at me with kind of a devilish grin.
In a playful way, she reached under me and grabbed my dick through my jeans. I not wanting to be outdone, slid my hand between her legs and grabbed her pussy. We played grab ass for awhile, doing everything sexual, short of actual intercourse. She stroked me, I fingered her. She sucked on my dick, I sucked on her tits. I wanted to fuck, but she didn't think it was a good idea.
That was my first sexual experience with a girl. She and I would eventually have sex. Later that summer we all went to stay at my grandparents 20 acre timber where grandpa had just finished having a cabin built. Us kids slept outside in tents. So after everyone was asleep, she and I snuck off and had sex.
All told, we had sex 9 times over the years, not including the first time where we didn't actually make it to sex. The only reason we stopped is because I got a girlfriend and it just didn't feel right screwing around on her.
She and I are still close friends today. We hang out and me and my wife do things together with her and her husband. To this day, no one knows that she and I used to have sex. Every once in awhile thought, I'll give her a look, or she gives me that look, and we know the other is thinking about when we used to fuck.