If that is not final yet, of course, your BF can make change

for that. But I think your BF and his EX don't want the child experience too much unpleasant changes in his life due to the parents' divorce. That might be the reason of your BF wants to keep the house for the kid. Again, that is up to your BF and his EX. Personally, I prefer not to get involve with any mater of my hu*****and and his EX.