Oodad - my heart hurts for you. I'm sure things will change with time, especially once your children become parents themselves, but I know that doesn't make you feel any better right now.
Just a thought. A first priority should be YOU. Keep yourself strong and healthy. Build networks of support and activities that you enjoy. You need to be completely whole and happy, so that you can be the best father you can be for your children when they finally realize they want a relationship.