But that's not what she is suggesting is the solution, she's suggesting they separate so DO can take him in.
@Flossyrocks
it does sound like it would be a very difficult thing to do, to take him into your family right now.
However, you separating doesn't seem like a good option either. Would it be possible to make some pigged changes? Such as DP working shorter/different hours so he's home pretty much whenever DN is home?
Maybe cresting a sleeping space for DN in the dining/living room. Something like a bunk bed where you can put the ladder onto the top bunk when he's at school so you don't lose space under it for your younger ones to play.& with a heavy curtain he can pull across/around it when he wants some private chill out time.
you may find if he lives with you & feels wanted & safe his behaviour towards your two changes.
i would try it myself in a 'we can do this together, but DP. must pull his weight. .he can't just leave it to you.
and ultimately if you can't make it work then you can separate later on, if you can't sort out a better solution.
at the moment, as it is, he would be forced to choose between staying with you & your kids/the baby OR separating & taking on his nephew. 😥.
woukd he even be able to do it alone? Time wise with work & financially??