As a real old fashion small gubmint individual freedom conservative, I don't see what gubmint is doing in marriage, anyway. It's a private matter. If two (or more) individuals choose to enter into a contract, the gubmint can and should enforce that contract, but it has no business trying to dictate the terms of the contract. It sure has no business changing the terms of an existing contract. (Changes in divorce law, alimony, child support, custody law, etc.)
Anything gubmint does, it does stupidly. I got a great example. I have known three different couples who got married legally who would not have been permitted to marry if the subsequent marriages of three OTHER couples had taken place previously.
In all three cases, a parent of one of the couple married a parent of the other of the couple, making the first couple step sibs. Since the first couple was already married, their marriage remained legal, but step sibs are forbidden to marry in my state although there may be no blood kinship.
Does this make a lick of sense to you?
While we are at it, there has been a great deal of nonsense talked lately about the "full faith and credit" clause of the constitution. It has been settled law for the last 75 years that a marriage not permitted by law in the home state of the couple is invalid if they journey to another state with more lenient laws to have the marriage performed and then return to their home state. Most of this case law involves minors, but some involved kinship rules and laws forbidding the marriage of epilectics.
(In the case of minors, the marriage becomes valid when the minor attains the legal age if the marriage has not been challenged before then.)