I was 9 when I first masturbated and got off. I started getting hair and getting erect a year before I just didn't know what to do with it yet lol. It wasn't until I stumbled across my stepfathers porn did I figure out how to masturbate (seen a guy jerk off on a girls boobs, and basically just mimicked what he did).
I hit puberty VERY young and always thought I was a freak until because none of my friends had pubic hair, and when I asked my best male friend about his penis getting hard he looked at me like I was talking another language lol.
Interesting enough a few years ago my father and I were talking about puberty and I found out he also hit puberty around the same age I did.