Well it depends on who out of your parents are you most like, if it's your mum then you'll be pretty much be the same size as her, if it's your dad then you'll probably be more like your grandmother. Please don't worry about these things! If you don't think about how you look (note NOT YOUR CLOTHES) you will most likely soar through life & people will respect you then there will be a point in your life when you will look in the mirror & no matter how you look you'll be happy with your life! Yeah..I might of gone overboard with this...hope this helps!
A lot of it has to do with inheritance. Because I look like my dad, did not know, as his mother died before I was born, but mom was smaller. My sister looks like my mom, so they are much the same size. It will depend on genetics
You can't really ever tell sometimes its genetics sometimes your just lucky so really you really don't know just like if your parents were bulit big then you will be mostlikely the same but just because if your parents are small and you are dosent mean you can't get fat just mean your very unlikely too but today whos really thin anyway sorry if this didnt help but its true
Is that important to you ? There is much more to a person than how big your boobs are. Big boobs, little boobs, that don't matter. It really is all about who you are not what you look like.