I grew up in Africa and although used to seeing people naked I never realised what happened to guys as they matured.
Anyway when I was 12 my brother-in-laws younger brother came to stay over as we were going on a fishing trip the next day. He was 15 at the time. Anyway when bed time came James was to sleep in my bed and I was on the floor next to him. We were having a riot recording noises and music etc. My sister ran through and told us to shut-up as we were making a heck of a racket. We settled down and talked in whispers for a while and then James asked me to rub his back as it was sore from swimming earlier in the day.
Anyway I'm rubbing away and exploring his body at the same time when hes says to rub lower, closer to his butt. He then says he is going to turn over cause his back feels better but can I rub his chest and stomach! This made me a little nervous as I had not seen him naked and I was getting aroused from all the body contact. He flips over and tells me to rub lower. I am aware by now that he has removed his PJ's and can feel his pube's. Although it was dark in the room the street light was still lighting the room and I can see that he is tenting the sheet. I 'accidentally' came in contact with his hard dick and he moaned a little I quickly said I was sorry but he said it was okay and I could continue. which I did. I was amazed at how huge he was in comparison to me I wasn't maturing yet. so this was my first time coming in direct contact with a teen male he was also uncut which was also a first for me. He tells me to rub his dick up and down which I did and he reaches down to play with me, this was feeling really great but my heart was about leaping out my chest in case someone walks in. Anyway after a few minutes he says watch out and the next thing I know he is shooting cum all over the place. I didn't know what had happened and thought he had peed himself but he quicky explained thats what happens as you get older. I was fascinated but grossed out as it smelt weird and the sheet was now wet and how would I explain this to my mom!
We did what we could to clean up. the next day we went to the lake to go fishing and James asked me to go for a walk with him this time I asked him to show me how he wanked and what his cum looked like we had a couple more experiences together. But this was the most memorable one.