We need a patriarch. That would solve a lot of problems.
The polygamists have the right idea in some ways. Let’s select one person who will serve as the guide for how the relationship will be arranged and everyone will try to align to that goal. Sure, there’s less individual freedom. But in sacrificing that, I bet you gain some harmony. When you have four people all with their own vision for where the relationships should go, it can be chaotic. A benevolent patriarch could serve as a leader with a vision for this unruly vehicle. He (because at least in traditional polygamy, it’s always a he) could be the arbiter of disputes, the person who makes the final decision when we just can’t come to consensus.