May I postulate that if you and your wife/family were the only existing humans that you would be the de facto "clanleader" and making the rules governing marriage irrespective of whether you had any religious convictions at all.
Marriage is not a religious institution, but a civil one and therefore under the purvue of the civil authorities, you know, the dread government.
Saying the state has zero right to regulate it is laughable, since it is the state (family law court) that is called upon to enforce it. (Hah, now they just preside over it's destruction).
And We, the people, through our elected reps have every right to define it and overturn the usurpation of the courts.
Your demands that the state get out of civil relationships is a non sequitur and not reality based.
Marriage is not a religious institution