First, breaking it may place you in legal issues, but secondly, it will just start the cycle all over again.
He has people in his life that he can talk to. He can talk to his parents, right? He must be living with them.
You are not his friend. If you were, it wouldn't have taken since Feb (your post about breaking up with him) to two weeks ago for him to respect your wishes for no contact. You wouldn't have needed a restraining order to get him to go no contact.
I'm very sorry about his nephew, and hope he gets well and gets the help he needs. I hope your ex gets the help he needs. But if you had to get a restraining order, that means it got ugly, right?
Protect yourself and your kids. That always comes first.
That you are thinking of doing this means it's time for some counseling. The co-dependency is real.
Wishing you all the best.
If the two of you have reached a state where a restraining order is necesssary, please re-think your motivation for wanting to contact him.