Marriage should be a sacred trust between two consenting individuals and, if they wish, their families and houses of worship, not individuals and the government. We are treading in very dangerous waters when we ask the government to regulate personal relationships, especially something with the religious overtones of marriage. To do otherwise, is the same thing as the anti-miscegenation laws in the 19th Century Southern States as well as the racial pollution laws in Nazi Germany forbidding marriages between Aryans and Jews. Government should not be involved in people s life style choices. The legal status of partners could be determined by contract between the partners.
Marriage is a religious institution.
Leave it to the churches. Frankly, if this same thinking was applied to other issues it might sound like the following. Government should not regulate running stop signs and red lights. Writing checks that you do not intend for your bank to honor. It is between the customer and the merchant and the government ought not be involved in it.