Is it possible to undo someone else’s bad Parenting?

My boyfriends exwife is a horrible mother.His son has cognitive/learning and emotional disabilites, and she has no interest in helping him she lets him do what he wants, because of all this, the child is not very pleasant to be around.(details in my other questions if u r interested) My BF wants him to move in with us, I am not ready. The boy is unpredictable and has been violent in the past. He goes to therapy on and off. The mother is often “too busy” to bring him regularly.
the boy is 12

Poor kid.

I can understand your caution – but also commend your boyfriends approach to doing the “right thing”.

Bad Parenting *can* be compensated for sometimes – and certainly if he finds he is with people that love him and try to help him, he may well prove less difficult than he is now.

He will almost certainly “test you” a little though – so if you do decide to try and help him, expect a few “interesting moments” along the way.

Big choice and not an easy one.

The simple answer to your question thought is “to a point, yes”, he could certainly benefit massively from being in a caring environment.