I've been saying the government should get out of the marriage business. Unfortunately, 'government' applies to 50 separate states, and invalidating 50 separate marriage laws is a tall order.
I believe people should be free to 'marry' inanimate objects, goats, or their dad's sister's niece or nephew. I've advocated domestic or household incorporation for purposes of accomplishing the various financial, insurance and inheritance statuses currently earned by married people. These hypothetical domestic or household corporations would have nothing to to do with sexual relations or the absence thereof. They could be valid for a limited number of members, perhaps 10. They would cover biologically related people, polygamous marriages or just friends. These people wouldn't be required to live with one another.
Marriage is a historically religious arrangement. Get the government's fingers out of it.