There is confusion over pack structure. There is probably no clear leader and the GSD is resource guarding something. I don't know what this something is without observation but its most likely you, your husband, or the other females. GSDs can get very protective over things if not taught properly to not have to protect them. Neutering/in tact doesn't matter, it's not for breeding rights, its for the attention.
Get them both into training, preferably together with you handling one, and your husband handling the other. Make them understand that they are equally UNDER you and your husband in the pack and that YOU will make all decisions for them. Lots and lots of obedience is needed. No high value treats/toys when they are together, and for now I'd just keep them separated all together.
My boy can get very "protective" over "his" females. They're not even my dogs...just female dogs at the club we train at (they've grown up together) or neighborhood dogs that he always plays with. He will put most males that "challenge" him for their attention in their place if I would let him. It's a bad habit, but I have enough control of him that I don't let him do it. I also don't have another dog in the house yet so that I could train him not to do so on a consistent basis (and borrowing the neighbor's dogs for this isn't going to happen).
CD RE TC HIC 7/10