I have several concerns. If he is unhappy at home, it is HIS job to fix that. He has to decide how he can be happy and he has to do it in a way where people don't get hurt. It isn't your fault that he has to fix that but it is his responsibility to salvage relationships with his family. His son is part of this situation. You don't have a responsibility to them. You don't know really if he is happy and if he is telling his wife that he is unhappy. You know what he is telling you. I fear that this may be an excuse to start an inappropriate relationship with someone he works with. I also fear that you may be setting up a situation where your job could be effected.
You have to consider that he is willing to cheat on his family and you don't know what he is telling them if anything. What does this say about him. It says if nothing else that he willing to be deceitful. You probably have your heart on the line but what is his investment in this relationship. You could also be setting yourself up for heartbreak when it comes time to choose. What will l happen when he has to make a choice. Is this worth it
If this has been helpful press accept