That's interesting about the weight thing. I was 15 when I got mine and was obviously one of the last girls in my class - I'd say the majority were in the 12-14 age group. I was also one of the skinniest so maybe the weight thing is true. I've also heard that you're fertile for about 25 years after your period starts. I don't think your fertility automatically disappears when that 25 years hits BTW just that it may start fading afterwards.

I think DSD got hers at about 11, definitely by age 12.