Hi Sol! I'm very sorry that your family is going through such a difficult time. No one can really help from afar. I'm sure you'll work things out: for your nephew, for the children, and yes, for their mother too. Because that's who she is. In a few years' time, the kids shouldn't look back on their relatives and think that they weren't able to solve problems in a mature way...

Maybe the two of them could draw up a contract: who gets to keep the house, how will the other partner be compensated, who will take care of the children, when and how often, how will they present themselves to the outside world, who will receive what kind of alimony...? If they stick to it, if they deal with each other objectively, they might even become friends at some point...