My father, and everyone on his side of the family, is large (and has been for several generations). My mother was thin until her 40s but is now overweight. Everyone on her side of the family is quite slim (and again, they have been that way for generations).
My sister has always been thin, even after giving birth to six (!) children. She works for it, though - she eats healthy and exercises. One brother has always been a health food freak and very athletic, and thus, slim. Another brother has fluctuated between being overweight and being a healthy weight. And my youngest brother is obese, and has been chubby since the day he was born. My nieces and nephews are all thin.
So it's really all across the board for my family. I definitely take after my father, though - from appearance and body build to personality - so I know I'm genetically disposed to struggle with weight.
(Sorry for invading the men's corner of the forum.