Does it also take a village to keep a couple/marriage together?

Only if you're the village idiot. The same one that allowed the villagers to raise your kids. You see how THEY turned out.

I would think not. In fact, I would imagine most people wouldn't want to be involved. Our romantic relationships are typically considered our personal business, and it's kind of awkward when that drama is brought to others.

no but it would be helpful if the in-laws learned to stop causing problems

No. That's their decision.