This happened to me a year ago, I was 17 at the time. I have a friend, who is 3-4 years younger than me, making him 13 or 14 at the time. He'd always joked that he was stronger than me, and one weekend when we were in my house alone, I told him to prove it.
He said that he would, and we decided to wrestle each other, best of 5 matches, and to win you had to pin the other or make them give up.
Anyways, we started, and all the body contact was really kind of turning me on. However, sadly, he beat me three straight times and pretty quickly. He is just a really strong person, and has had training in wrestling.It was embarassing though , After the last one he just sat on my lower stomach just above my crotch.
He told me that because he'd won, I should do something for him. I asked him what it was he wanted me to do, and he just looked at me and said 'jerk me off'.
Now, I'm not that small, I'm a bit under 7 inches long, so I jokingly said 'Fine, I'll jerk off your tiny cock'. He said 'Bigger than your's'. So now I was curious, so I agreed to do so.
He lay down on the couch (we were in my basement), and unzipped his jeans, and pulled out his cock. He was soft, and I couldn't believe my eyes. He was almost 5 inches long when soft.
He asked me what I was waiting for so I got on my knees in front of the couch and started playing with his cock. He quickly got hard and this kid was 8 inches long, and really thick. I continued jerking him off until he shouted 'I'm cumming' and shot all over his shirt.
Sadly, that's all that happened, as he went to clean up. I ended up taking care of myself when he was gone.