The government does not hand out “friendship” licenses, loving as that relationship might be. They do not issue “roommate” licenses, regardless of how close the pals or girlfriends are. Nor do they give out licenses for sisters or brothers to cohabitate, doting and faithful as they might be. They give out marriage licenses. Why? Because the sexual union of one man and one woman is the relationship that (in the vast majority of circumstances) produces children.
And children have rights and parents have responsibilities. It is this fact, and this fact alone, that makes this arrangement, and not any other social arrangement, subject to governmental sanction and regulation. This relationship must be codified in law—parents bound to each other and both of them together bound to their children. No man has any kind of legal claim on a woman married to another man, and vice-versa, and no person has a claim on somebody else’s child. It is the legally codified institution of marriage that sanctions and protects these relationships and the freedoms and responsibilities they entail. “Love” does not a marriage make."