genetics?

I think so, because my mom and sis are overweight, but folks tell me I'm very thin, even though I don't think so. My hair is baby fine and wavy, but mom and brothers is thick and curly, my sisters is super straight and fine.

does anyone else here have really fine hair while there brothers and sisters have really thick almost nappy hair? i do and im starting to think it has something to do with my diet cus coincidentely im also the only skinny one in my family. could this be a connection? cus i honestly know very few underweight people with thick hair, on the contrary i know very few overweight people with fine hair.