Shades of racism here too. The western nuclear family is not the only model here.

This also, I would note, discriminates against polyamorous people as you can't be married to or even have a domestic partnership with more than one person. Polycules who want to live together have other problems too. (Or even who want to exist...there are places where being in a marriage-like relationship with more than one person is a felony. States you would think of as relatively sane).

This rule might have affected me too...for a while growing up I had a foster brother. It wasn't an official arrangement...Dennis' parents were going through a particularly acrimonious divorce and fighting constantly, so he stayed with us for a while while they got everything sorted out. Oddly, I don't remember which parent ended up taking him home, and I don't have much contact with him now because of emigrating and all, but I know he came out fine.