Sounds very ancient RomeLol what's so unrealistic about monogamy? It's a beautiful thing. Soul-mate, better half and all that
This is why marriage is so important as a social norm. The commitment that the couple make is to themselves, to the community and to God.
There must be crushing social pressure placed on everyone to (a) get married and (b) stay married, lest you be socially ruined by being labeled a fag or hoe
The second you start making concessions against this, all of society starts to crumble (hence: now)