See this is why when the MC plans to reform the cult, one of the biggest things he wants to change is the 6 clan system. The leader has to appease the 6 influential clans by giving each of them a "chance" to have their bloodline become the next leader, which means that there has to be a potential heir from each. Thus there have to be 6 wives at least, and any wives for love from outside the clan will essentially be destroyed because the 6 clans won't tolerate a rival, and they spend the whole time sniping and fighting each other for influence and raising their children on the poison of hate and competition- Even the heirs FROM the 6 families are squabbling amongst themselves! They're siblings but all they do is plot for each other's downfall or death. The one exception being the one female heir at the beginning who gives the tip off, but not because she cares about her brother, she just doesn't want to lose face, and he still doesn't believe her at first because it's too likely to be a trap. They're siblings. And from this, this poisonous den of backstabbing and vengeance and revenge and hate and pain- The last survivor becomes the next leader and is told they have to do it all over again. This does not make sane people especially when they're also being pushed to their limits in all sorts of other ways.
I'm with the MC. The six clan system has to go, and since the clans will never willingly give up power, he has to break them.
And then be monogamous!