I would try a training class together. that way they are in a controled environment and you can work with the trainer to address the issues they are having with one another. Exercise also helps a tired pit is a good pit. If you have someone else that can help you take the 2 of them for walks together. dont give them time to get aggressive just walk at a fast pace so they get used to each other but you have to do this on a regular basis and eventually with some work you can have 2 dogs that get along. I have 6 and I’ve hhad some problems but I never let it get to the point that they actually start fighting. If you watch myou can pick up signals from them and prevent stuff before it happens. but a calm assertive approach is needed. If you are nervous and fearful they will pick up on it.