This happened a few years ago. My cousin came to visit me after school one afternoon. We walked around the yard a little talking and doing a few tasks. When our conversation changed to a Q and A session.
He was asking the questions and I was giving the answers. We were about six years age difference. When he started to ask questions about masturbation and what it was and how you do it, as his dad never told him anything. As I was a frequent masturbator I told him everything he wanted to know, even showed him a few moves. We kept on talking and later that day we ended up in my room talking and reading through some porn mags totally naked.
Not long after I noticed my cousin was hard and I myself was very hard. I asked him if he would like to masturbate as he has never masturbated before in his life. So we got going and he wanted to jerk me off, so I said ok and he started. He was 13 and it did not take long for him to cum, he was a little shocked, but we got together every day to masturbate two to three times. I am now married but we still get together for some masturbation fun.