I was fully ready to have sex when I was 14. My mom took me to Planned Parenthood when I told her I was thinking I wanted to have sex soon. I really wanted to sleep with my long-term boyfriend, but he wasn't ready yet (he was a year older). We waited a year and I was 15 when I lost my virginity to the guy I ended up dating for five years, along with his girlfriend and a fourth guy in a committed poly relationship.
To be honest, if I had had a boyfriend before that, I probably would have had sex at 13. I was a sexual little creature. I was masturbating at 5, or as long as I can remember. My parents were hippies and never taught me that sex was bad. I never had my bodily integrity violated (aka no sexual abuse), and I always felt in complete control of my body and my sexuality.
If at 13 I was offered the chance to fuck Sting, my Number One Crush at the time, you BET I would have. In a heartbeat. Of course that's not the kind of artist he is and I never made it to groupieland. And that would have been a more societally questionable situation than me and my 14-year old boyfriend. But I stand by the enthusiastic consent that I would have given.
Make of this what you will. I don't pretend to know what happened between a rockstar and a 13-year-old groupie decades ago. All I can do is offer my own experience.