Livre d'Or

Make no mistake: the inherited obligation style family when considered as elder care is very much an intentional community, just bred not brought; if you do not build one successfully -- whether through ineptness or misfortune -- you are as bereft of care in old age as is anyone who failed to construct a family on the basis of negotiated commitment.

Yes, this! The same applies to many of the other facets of inherited family: it works because people chose to maintain it, to teach those values to their children and relatives, to tolerate/minimize/outright endorse the obnoxious or dangerous characters in the name of family, and to lean gently or coercively on other members to maintain it. Families are just as prone to the "geek social fallacy" as communities of interest are, except family is usually articulated in terms of responsibility rather than inclusion.