I think around 13-14. I got mine at 14, but lately girls are getting them earlier and earlier. My sister got hers just after she turned 13, and some of her friends got them at 11 and 12. It also depends on your mom though, for example, my mom got hers at 14 so my sister and i got ours at around the same time. Genes also play a part in when you get it
the age range is anywhere from 9-16 years old I was a "late bloomer" I didn't start til my sophomore year in HS but it's normal according to my doctor I was fine down there so if you haven't started yet don't freak out like I did you might just be a "late bloomer'
Normally when girls start Developing upper area, and hair in different Areas, they are close. It also can depend on you mom. Ask her when she started, maybe that will give you an idea about what time. Hope this helps!