Thanks for the advice. We do have more than the two cats I mentioned, seven in all. We do have the room to keep them separate if needed. We do give them all individual attention. There's plenty of food. Like I said, this just came up. The youngest cat and the other cat have been together and kitty buddies since March of 2010. None of the cats goes outside as we've seen foxes and heard coyotes in the yard. We don't want to isolate anyone, but don't think the other party should have to be scared all the time. Today I put one of the cats in one room for a couple hours, let him out. Then the other cat tried to jump him, so I put him away for a couple hours. I've just done the evening snack time ritual and they all seem to be leaving each other alone for now.

For a little thread drift, these are smart cats. They all know the term snack time, when we say it.