On one hand, I can understand polygamy. Why limit yourself to one sexual partner? As long as shit's happening between consenting adults and one of them isn't trying to slather themselves in shit or something you're good.
The point here is that as far as I'm aware, none of these people are having sex and their relationships are merely performative. Something to validate themselves and go "Aha! I'm dating someone!" which really just boils down to them merely having roommates they've had one or 2 awkward sexual interactions with.
Edit: I think a more accurate description of my first point would be a FWB or Open Relationship sort of deal, as having more than one partner that is more than just a friend you occasionally dick is a lot to handle. Sorry guys, I just woke up!