There's a saying that goes we choose our friends but not our family, but is this strictly true? The idea first occurred to me when my uncle divorced my auntie, and suddenly my auntie wasn't my auntie any more. I had a new auntie, my uncle's new wife, and my old auntie was no more. She wasn't even the ex-auntie. Aside from parents and siblings, this can happen with other members of one's extended family: husbands and wives, aunts and uncles, cousins and all the in-laws.
As for friends, do we even choose these? What if I wanted Brian Eno or Martin Amis as friends? Would this be possible? It's doubtful. No, friends, unfortunately, are just as much a product of environment and chance as family is.