Remember, too, that just like people, cats sometimes just don't like each other. I had two that were litter mates, and hated each other until the day they died. They never snoozed together, or even in the same room, much less groomed each other. I could not put them in the same carrier without them tearing each other up, and even at the vet's or being boarded, they had to be in seperate cages. I could never figure out why. But the did coexist peacefully as long as they were never forced to come face to face, and they were both very loving, affectionate lap kitties, as long as they didn't want the same lap at the same time!