Don't know if he is interested or not.

Work with him on this. He is hurting and needs to process the pain of losing his dreams, etc. Be his friend and let him know you are around if he is interested. He may be catching flack for having you around, especially if their are custody concerns, etc. It may be he wants to protect you, or thinks you are better than he deserves, or not a possibility for someone like him. Let him know he shouldn't make decisions about you, without you, because that is disrespectful to you as a person, much less as a friend. You are both precious in the sight of God, and he might have forgotten that, if he ever knew it. Find ways to listen to him and see if you can earn his trust so he will open up and let you be part of his processing.
Don't judge either party. If he feels like you are biased toward him, he may want to protect her through the children. He may also want to put this part of his life behind him before starting something new, so the two don't intersect and cause even more confusion. That is probably the more mature option but, talk to him and see what is going on. Talk and person so you can see his non verbals as well as hear his verbals.