Sibling Rivalry

Question
I have 5 indoor cats. 2 of the cats are siblings and have been hand raised together since they were two weeks old and are very attached to me. One of the siblings is a male, the other is a female. They are now two years old and both get along well with all of the other cats. The female sibling, however, often attacks her brother, while the brother tries to clean or play with the female. Whenever the male siblings receives attention, the female attacks. Whenever the male sibling is sleeping, the female attacks. Whenever the male sibling meows, the female attacks. Sometimes it seems like an attention thing. The female sibling did not do this before the male sibling's surgery- foreign string body. The male sibling is smaller than before, but has always been very mellow, not aggressive, and very friendly with all the cats. All cats eat together at the same time and get plenty of attention. How do I solve the problem?

Answer
Kathleen,

More than likely it is because your male cat went to the vet. You didn't say how long it has been since he had the surgery (poor kitty!). When a cat comes home from the vet or a vet hospital, it brings home many different smells. The smell of other cats, medicinal smells, antiseptic smells, anesthetic smells, etc. all clinging to its fur and absorbed in it's skin. Cats go by smell in recognition, not by sight, so the female more than likely thinks that since the male smells different that he is a 'new' cat and an intruder. When the smells are gone from him completely then she should settle down.

I would keep a rolled up newspaper handy and when the female starts picking on the male, I would whap her with it saying loudly "leave him alone!". Cats go by association and you want her to associate the newspaper with her aggression towards the male. Let her know that her behavior is not acceptable. The newspaper won't hurt her, but the noise should scare her. Wait a few minutes then love on her. You want her to be afraid of the newspaper, but NOT afraid of you. She should get the association soon and then all you should have to do is pickup the newspaper and say "I said NO!" and she should think twice about being aggressive.

Try giving both cats a special treat, like a can of tuna. Feed them next to each other so that being together is a pleasant experience and not a negative one.  

Tabbi