I enjoy reading the stories about how guys learn to masturbate. My story is similar to some others I've seen here, but maybe worth posting.
My brother was two years older than I was. Our house was really small, and the two of us shared the only room in the upstairs. We didn't have air conditioning up there, so in the summer it was very hot, and we'd sleep naked on top of our covers. In the winter we had no heat, so we'd cuddle together in his bed to warm each other. I liked both. So much that even if it wasn't hot, we'd both sleep naked, which felt neat. Since we slept naked, neither of us was shy about letting the other see us in that condition, so nudity wasn't a hidden thing in our bedroom.
When he was 12 and I was 10, my brother started masturbating. I didn't know if someone had showed him (I suspected his best friend had, since they had been sneaking off alone a lot recently), but one night I looked over and there he was, rubbing his penis up and down between his thumb and forefinger. I could tell he was enjoying it, and from playing with my own penis, I was familiar with how good it felt to get it hard and play with it. I just lay and watched him openly, fascinated at his intensity, especially when he reached what I was to find out was climax. He stiffened and held still, with only an odd jerking in his crotch. Then he'd sigh and relax, breathing heavily. He didn't seem to mind that I watched him, and I found I had a boner, too, which I played with as he did it.
He did that almost every night, and I watched. Pretty soon he began shooting his sperm. Just a little at first, but it got to be more and more. Then one night he said, 'Why don't you do this, too? It feels great.'
I thought, 'Why not,' and started to mimic him. It didn't take long to realize this was a lot more than just idly playing with my boner. It started feeling really good, and then my first orgasm hit me. Like a ton of bricks. I yelled out, and my brother hushed me, saying that I'd wake up mom.
I was amazed by the feeling, and sorry that I hadn't tried it sooner. From then on, we both did it each night before we went to sleep. I found myself looking forward to it with great anticipation, and that thinking about it gave me a boner in the daytime. I'd slip away in the daytime and do it when I could. I had a little spot in the garage where I could hide and do it. I found some used Kleenexes hidden there, and realized that my brother (and his friend?) used the same hiding place.
I finally did find out that my brother had been doing it with his friend. I came home from a friend's house early one Saturday afternoon and caught them with their pants around their ankles in our room, going at it. My brother wasn't upset, but his friend was embarrassed to be caught in that situation. I decided to join in, so lay down on my bed and pulled my pants down and starting doing it. So the three of us did it together, and that was neat. That broke the ice, and they stopped sneaking off, and instead did it in our room, even when I was around. We frequently did it together. We didn't have to hide it, since our mother NEVER came upstairs, so we could do it any time we wanted, which was all the time.