When I was a lot younger, me and my brother and my cousin were obsessed with cocks (as you are at a young age). We would play dares and dare each other to do stuff naked, like walk around the room or something like that, just so we could see each other's cocks!
Then my brother went through puberty and his cock grew and he got pubes. We were still obsessed with cocks and he let me stroke his shaft until he got hard and I countinued to play with it. We were young and didn't really know about sex and wanking, so he never came. However it was a good experience all the same.
My cousin and brother are older and wiser now and so don't like showing off their cocks to each other. What a shame.