they were already bounded by some slave contract or whatever, they should just do the same and have some magical contract that binds them as a couple instead of this low level marriage with only a paper as proof. That only applies to us peasants who don't have magic powers and relies on its legal benefits. They could just rule in their own countries and still be a couple, producing children as heir for their house/lineage. Let's break the norms, it's fantasy anyways
Cats are polygamous while wolves mate for life, which means Nemu gets two in one while the two gets one for life
Wait, no. It's making so much sense that it's hilarious