At what age will breasts stop growing and will mine ever get bigger?

I am only thirteen and i am a 34a..but most of my friends are already 34-36 d's and im like the only one.. I first got my period a year ago, and my moms side of the family is big chested, while my dads side is small chested. I defintley would NEVER consider getting any type of surgery when im older!! Please help thanks :)