When there is doubt as to the validity of a marriage, either party may, in a court of equity in a county where either party is domiciled, demand avoidance or affirmance of the marriage, but when one of the parties was under 18 years old at the time of the marriage, the other party, being of proper age, does not have a proceeding for that cause against the party under 18 years old. The judgment in the action shall either declare the marriage valid or annulled and shall be conclusive upon all persons concerned with the marriage.