It can be legalized, then only the faithful and the truthful couple will remain and be tied forever.
It will be so complex for the state to contend if the problem goes down into the individual level there millions of factors and tendencies to consider and weigh upon, mostly if justified rights are clashing with each other. Let each and everyone have that freedom to gain happiness in marriage as they wish but more substance should be given to those who are greatly affected which are the children at this instance the state should intervene.