That's how you can tell this isn't in the US. Though there are financial reasons why divorced people live together, standard procedure is often for the divorce lawyer on the female side to file a restraining order (in this case easy since the husband punched the father in law) and get the husband dispossessed of the house in said order, which also has the benefit of de facto putting the kids in the custody of the mother. During the divorce this is also used as leverage.