Just wanted to give a conclusion to this thread. We ended up giving the sisters back to the girl we got them from a month ago. She took them back to the house where they were raised, which was her deceased father's house, for a month. Her plan was to take them in when her and her boyfriend got an apartment, which should have happened by now. We don't get updates, partly because it would be sad and mainly because she's a friend of my wife's sister. She did tell us though that the one cat that was having litter issues didn't have them back at her original place and she also reconfirmed that she never acted like that before we had them.

I guess it was just not going to work out given the personality clash. I was using the Feliway spray for a few weeks but it really didn't change the behavior. The final straw was when we were repainting our dining room in late August. I had drop cloths laying around for a few days and when i went to pick them up, I found **** and pee in and underneath them. We washed them and the next day I layed them down to paint again and right in front of me, she took a dump on it. That was it.