How is this fair?

My sister has a family, a house and a decent income. I have two cousins of similar age to my sis and I. One is stunningly beautiful, the other is a genius (I mean that literally). I am average in all ways except my income which is shockingly low despite my best efforts! I have tried for 2 years with no luck for a baby with my bf (who, I have to say, is fab). How, genetically is it fair that out of the four of us, we have a natural mother, a beauty to rival aphrodite, a pretty little genius scientist and a barren, plain, bog-standard me?! Wah! :-(