Hi, Sarah!
Sounds like you have your hands full!
As someone who has lived through divorce and has also grown up in a "mixed" family, I can tell you there is great emotional stress. (Not that you didn't already know that.) My point is that these boys don't the emotional maturity to deal with all of the adult baggage that goes with divorce. I feel for you having to deal with it because my step-mom did too and it was very difficult!
Here are a few suggestions:
Sometimes bed wetting and emotional stress are connected. The first thing then is to be patient and understanding. It may be he is feeling a lack of security for some reason.
Secondly, address the physical. Try simple things first like not allowing anything to drink after a specific time at night. (This worked for me when training my own children.) I would usually stop allowing drinks about an hour before bedtime until I was confident they could make it through the night. Observe his patterns during the day. If he is drinking a lot and peeing a lot during the day, this may mean he has a more serious problem. (This is one of the tell-tale signs of type 1 diabetes,as I found out with my three-year-old daughter.) If he is a heavy sleeper he may not be aware of his body needing to relieve itself. Maybe he is just a chronic bed wetter. Some children do this until their pre-teens. In either case, maybe a visit and a chat with his doctor may not be a bad idea.
In any case, take heart. I will keep you in my thoughts and prayers.
Sincerely,
K. Larson