Big breasts but small butt... help?

Ok so I'm 18 and I weigh 105 pounds and I have big boobs (around C to D cup), but a small butt (with small legs/thighs and narrow hips). How can I get my butt to be more big so it can be proportional to my body?
Most fat goes to my stomach and boobs first, so I don't think eating a lot would help unless I would want to become fat. I already have some belly fat.
I would just like a proportional body... preferably with my butt being medium sized rather than small.
Updates
+1 y
Also when it comes to my genetics, my mom and dad were very skinny when they were my age. However, now they are overweight. My mom has big breasts, a big stomach, and a big butt but I do not want the big stomach lol...
Big breasts but small butt... help?
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