I think it was W.D. Hamilton- not the equation guy but every other W.D. Hamilton that ever existed- who noticed, as we all do, that the more closely someone is related to you the more they want to freeload off you, talk shite to you and generally fuck with your mind. This is called altruism. The same goes for anyone who works for an organization which insists its drones add Father/Brother or Mother/Sister as a prefix to their names.
The more general question is why big words like altruism squint up at repellent, up their own arse, eggheads with the eyes of an enamored but inexpert blow job delivery system while remaining the dazzling debutante who blanks the doormen and limo drivers and bouncers who, obsequiously securing her privileged status, seed but her rectum.