State laws regarding marriage arose because of paternity regarding children. Instead of being about marriage, they should be about paternity.
If government wasn't already discriminating against individuals (based on their marital status, and the number of children they have), then gays wouldn't be asking government to recognize their marriages. Married people pay different tax rates than singles. Married people get Social Security survivor's benefits, gays do not.
Rather than debating whether government should recognize gay marriage, we should instead insist that government not discriminate among individuals based on their marital status. Laws regarding children should revolve around paternity, not marriage.