It's because everyone in my family has small breasts and they grew before their chests developed

Look, breast size varies a lot from person to person, and it's usually related to your family's genetics. It's super normal to have small breasts, and that doesn't mean anything about your puberty or your menstruation. Like, every body is different, you know?

Breasts start to develop right at the beginning of puberty, and it's one of the first signs that things are changing inside. But "chest growth" is a process that takes time, it doesn't happen overnight, and it can continue for several years. The first period usually comes after breast development has already started and other signs have appeared, like white discharge in your underwear and the growth spurt (when you grow a lot in height).

So, even if your family has smaller breasts, that doesn't change the fact that your breasts will grow in your own time and your first period will arrive when it's time, okay? If you want to know more or less how long until your first period, there's a really cool quiz here on the site: how close is my first period?