The United States constitution should be amended so as to remove all references to marriage. All of the usual legal implications of marriage, as granted, enforced, and operated by the government should pertain only to civil unions, which would continue to be managed by the government and defined as a legal arrangement between any two consenting adults. Marriage would then be relegated to a private religious institution to be presided over by separate denominations.
If two consenting adults desire a legal partnership for legal purposes, such as establishing next-of-kin, visitation, and estate rights, they should seek a civil union from the government.
If someone wants a symbolic, religious arrangement with another person, they are free to consult a religious institution of their choice.