I have to same problem. Only over certain things though...
Merrick Flossies
Any type of biscuit
Any and all toys
TJ want EVERYTHING to be HIS and only HIS. He will attack Roxy until she releases the item and he quickly takes it, usually it happens so fast...BUT Roxy will always SCREAM when he attacks her, she sounds like a human screaming for help. I usualy pick Roxy up and then TAKE AWAY BOTH items that caused the fight. And then there are other 'treats' that TJ stands NO CHANCE of getting and he doesn't even try. Its so weird! TJ is crazy too! Roxy remembers though which things she will get attacked for and she doesn't even bother taking them from me anymore, its so sad.