Aggressive behavious

[gccm]

Hello. I have two eight year old castrated male brothers who have always gotten along. All of a sudden yesterday on cat became aggressive to the other, growling and hissing at his brother without provocation. The cat on the receiving end of the behaviour becomes curious when his brother starts acting up but doesn't do anytthing aggressive in return. Any ideas what could have caused this?
We have a third cat, an older female who is the boss. She went to the vet yesterday and cat #2 cuddled with her when she returned. Is it possible he picked up other pet scents that she picked up at the vet and this is the reason his brother has turned aggressive to him?

 

[molly22]

Hi. Oh yes, the smell of the vet probably scared your cat. One of my cats hisses at the other when he comes home from the vet. Once the smell goes away all should go back to normal.

 

[gccm]

Thanks! I'm hoping that's just it. How long should this last? It's been about 24 hrs. And I hope the aggressiveness isn't being done to the female who went to the vet because she's the alpha of the house. Perhaps the cat being aggressive is responding to his brother because they've always been equals and now he smells different?