I have had cats all my life. I don't think it's fair to isolate one, or have them lead separate lives. In a situation like this, I'd grit my teeth and let them work out a pecking order between them. Eventually, they will reach a status quo. Unless blood is being drawn, or real terror caused, give them time to make an adjustment themselves. You say "Two of our cats..." Have you others as well? I've never had fewer than three, and often five cats at a time, and I'm always careful to give equal amounts of affection and attention to each. Cats are very jealous, and will beat up a 'favoured one' if they can!