One time last year my 11 year old cousin came to visit. I was 13 at the time. We slept in the same bed. It was the middle of summer and really hot outside. I suggested since it was really hot we both sleep naked. He said 'Ok' and we both took our clothes off.
After about three minutes I asked him if he had ever masterbated before. He said 'No'. I asked if he wanted to learn, he said 'Yes'. So I turned on the light, went back to the bed and took his small cock in my hands. It got bigger quite quickly, so did mine. We were both uncut. It took him about two minutes before he came all over me. We did each other a few times that night, now everytime he visits, we do it.