It will happen in time

If they can't let go now, then it will eventually happen. You can't keep up with that kind of mental anguish for years and years (even though I've seen long term, horrible relationships). They all ended, some in divorce, some in permanent seperation. At some point one will say, enough is enough.

Yes, I would urge you to stay out of it. If they both confide in you, you will have neither as a friend when that happens. It can also pull you down with the negativity.

One thing I learned after a long life of mistakes is to stay away from major negativity. Some family you can't avoid, but you can limit the exposure. Even if they are not aware they are doing it, they will try to get you to take sides. And in the process they will bring you down. Be cautious.

Molly