Maelakin, run it through the legal test I stated. While a distinction based on sex does not have a social purpose, one based on consanguinity (blood relation) does. It is well known that close relatives having children often results in mental retardation. Now, a marriage/civil union is not only a business merger. For a pure business merger, form a partnership, which is the legal entity for business partnering. Marriage/civil unions are a financial and social partnering, involving the same household most always, and involving consumation of the marriage/union in sexual intercourse most always. While each of these characteristics may not appear in all marriages, they are common to the vast vast vast majority.
Accordingly, the consanguinity rules, as well as the binary nature, should stand. And should not be threatened. Especially right now, when doing so will only raise the spectre of the "parade of horribles" that conservatives are afraid will follow.
PS, you guys need girlfriends.
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