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My name is***** and I am sorry to hear that Macky is having such difficulty getting along with his sister cat. It sounds like a severe "fear event" started all of this and helping him through it may be very difficult. Have you considered taking him to see your vet? It sounds like he may need something stronger than just the over-the-counter remedies that you have already tried. Prozac can be very helpful in managing anxiety. He may also have some underlying pain from the fighting so a physical exam to determine if there is any residual pain can also be helpful.
You may also consider taking him to a Diplomat of the American College of Veterinary Behaviorists. These are veterinarians who have gone to three extra years of schooling to learn about dog behavior and specific training and medications (if needed) to help remedy undesirable behavior. To find a specialist near you check out their website at www.dacvb.org.
I hope with appropriate behavioral therapy and medications, you will be able to get your kitties back together again.
Does this help? Do you have any other questions?