Some data from Canada on why same-sex couples get married:

According to the census, nearly one in four lesbian married couples in B.C. (24 per cent) have a child living with them, compared with just 13 per cent of lesbian couples living common-law.

Gay men are far less likely to have children than lesbians.

But they, too, have a big marriage gap, with 6.8 per cent of gay married men living with kids, compared with just 0.5 per cent of unmarried gay couples.

How does this undermine civil marriage for heterosexuals? How does it harm society? Isn't it better for children of gay couples to have the legal and social security of a marriage? Isn't legitimacy better than illegitimacy? And doesn't this pattern actually enhance the conservative argument that marriage is primarily for the benefit of children? I guess that argument doesn't count for much with some when lesbians make it.

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