For starters: * Members of a couple (same-sex or opposite sex) have family obligations to their partner's extended family. * A surprising number of same-sex co

For starters: * Members of a couple (same-sex or opposite sex) have family obligations to their partner's extended family. * A surprising number of same-sex couples have biological children from earlier relationships. * The "traditional nuclear family unit" is not that old a tradition - prior to large-scale industrialization and easy migration, extended families were the rule. It's just one kind of family. Others exist.