I hope your injuries soon heal. This often occurs with two litter mates when they live in the same house, they get to a certain age and there is trouble. Inter house fighting is always a difficult one to deal with, do your dogs socialise well with other dogs outside ? Do they get chance to be apart from each other when out for a walk etc. I would contact a behaviourist prior to getting them castrated, to check it is the right thing to do.
Jen