This is a hard place for you to be and I have similar issues with Oliver and Charlie (two of my furry ones). I had reached the point where I was ready to return Oliver to the shelter I got him from. He was always good with the other guys and me, but the minute he would see Charlie he would try and fight him. Before that I did a couple of things, first I had Nancy (an animal communicator) do a reading on both of them. It helped me understand a little better some of this issues going on. That wasn't quite enough, so I ended up putting Oliver (he was the aggressive one) on Prozac and it is like night and day. I normally wouldn't have gone this route, but I had tried everything and this was the last resort and boy did it make a difference. He now "reminds" me when I need to give him the medicine