Thats terrible about his mother,really...I know that he was attached to her and all that.
I'm terribly sorry for him.
But remember that you didn't leave him because you felt like it.You didn't do anything wrong.You don't have to feel guilty about anything.
I know that it must be terrible for him to be left all alone,with no family.
But maybe this truly helps him to look at things from a different perspective.Life is so fragile and he is going to have a child soon.
This could cause him to re-think his actions.
But you don't have to apologize or feel guilty.He chose this.He treated you terribly.
It's sad to say but maybe there is a silver lining in his mothers illness.I truly hope...
