Dr. Borchelt recommends not paying too much attention to your cats individually but really laying on the strokes when they're all together. Make a common bed. Cats that sleep in the same area will gradually get used to each other, which may help keep aggression in check. Dr. Borchelt recommends putting a bed for each cat in a comfortable, favored spot, like near a sunny window. If your cat is repeatedly spraying in the same place, applying a pet repellent may help turn him away.
Many vets recommend repellents containing bitter apple.
While pet repellents can help protect certain areas, they are unlikely to stop the spraying, Dr. Borchelt adds. Eventually your cat will probably just move on to a new area, and you'll have to start the process all over again. Do a deep cleaning. If you've recently moved and your cat has just started spraying, it may be that he smells traces of other cats. Dr. Borchelt recommends scrubbing the rugs with a combination enzyme and bacteria cleaner, like Outright Pet Odor Eliminator or Nature's Miracle.