I see from the posts here that a lot of boys learn to masturbate from seeing their older brothers do it (or friends or cousins). Here's my story.
I grew up, like a lot of other boys, sharing a room with my brother. He was three years older than I was, and we had a very open relationship. When he was about 12, he discovered masturbation. I'm not sure how he discovered it, but I always figured it was his friend, James, who was always making open comments about things like that.
Anyway, one night I noticed my brother rubbing his penis in bed on the other side of the room, and he seemed to be enjoying it, and came to a climax where he stiffened and held still, breathing hard. Nothing came out, but it was an interesting sight.
He started doing that regularly, and made no effort to hide it from me, but he did always lock the door. After several months of that he started to squirt a small amount, and I found that extremely fascinating.
We each had a desk in our room to do homework on, and after a while he started stripping his pants off and doing his homework in just his boxers, and often would stop doing homework and masturbate right there in front of me. He'd do it through the fly of his boxers for a while, then stop and pull them down his hips, and continue 'til he came, then clean up and finish his homework.
I was still puzzled about why he was doing it. Sure, I knew that it felt good to play with my penis, but I didn't know about an orgasm. Then one day (I was 9 then), I decided I'd try to do it like my brother to see what the big deal was. And boy, did I find out! I had been getting aroused every night when he did it, so when I started stroking like he did, it felt really good and I continued to do it. It started to feel like I had to pee, but I had just peed a little while ago, so I kept it up, then WHAM, it hit, and I had my first orgasm. I was so surprised that I made a loud squealing noise, and my brother laughed. He had been watching me, stroking himself the whole time. When I came down off my orgasmic high, I told him that now I knew why he did it all the time. He said, 'Yeah, it's great, isn't it?' He also said he was surprised that was my first time; he thought I had been doing it all along, but just hiding it like he used to. Turns on he had been doing it since about 8 years old, and one day got tired of hiding it from me, and just did it in front of me. He said it took him a long time to get up the courage to do that, but once he did, it didn't bother him, and he kind of liked it when I watched him. And he said it was fun watching me.
Well, from then on, we both did it every night, either in bed or at our desks, and enjoyed watching each other.