Moving across country: Should I leave me aggressive dog?

I agree with Vie, he might be traumatized from something, maybe he just needs attention and not share it with the other 2 dogs, all personalities are different human and animals alike. Get the behaviorist help and follow up. Some dogs are harder than others to understand but ultimately all dogs are to be understood. It sounds as if you love your dogs, extend the search and find a good behaviorist to help you understand him. If not, and it might sound a bit silly, call those dog training shows ( 'dog whisperer' or 'it's me or the dog' ). It takes time and a lot of patience. If you don't have the time and your brother truly cares for the dog and is willing to spend the time and give the love and patience then leave the dog with him. He might miss you in the beginning but if he gets the love and attention he needs he will be ok in no time.