there were times when I was 9 with another girl my age playing doctor, doing various things, lol, if that counts.
But first real sex, where we knew it was sex and what we were doing, was I was 12, she was 13, we found some of her daddys porn and watched it in the basement, almost got caught, If I remember correctly it was pretty awkward and I got a black eye somehow, lasted like an hour though, I just kept going and she wouldn't let me stop, both of our first times, just acting out what we saw on TV.