Resident cat aggressive towards new cat

[Kelseypolo]

Hello! I have had my first cat, Kevin, for about 9 months and he is 11 months old. Last week we adopted Cash, his litter mate and actual brother. Cash did not like Kevin at first because Kevin was very curious about him. Kev just wanted to play and engage with Cash. After a few days its seems the table has turned...Kevin is not liking Cash. He constantly instigates rough play/small fights(?). Kevin used to be very talkative to me and now he just walks around, silent or acts very sad/mad when I am around him. I know it has only been a week of them being together but will Kevin ever get back to his normal self? Is this just an adjustment period? I would hate for Kevin to forever be mad at me...we thought getting him a play mate would make him so happy as he always seemed sad at home when were were gone to work for the day...

 

[mnm]

My guess is Kevin has now realized his territory is not his own. Hopefully you’ll get helpful suggestions. Until then give him extra lovin. I only have one cat but she acts the same with visitors! She is fine when they arrive but once they stay overnight … she is in in full “this is my territory” mode.

 

[ArtNJ]

Two cats under a year, it should all work out and end in friendship.

Next time you add a cat you should do a formal introduction process. Not necessarily needed with cats this young, but with older cats, its asking for trouble to skip one. Here is a guide: How To Successfully Introduce Cats: The Ultimate Guide – TheCatSite Articles

 

[LTS3]

Even though they're brothers, they no longer recognize each other after a nearly a year apart. You need to to introduce them together like they are two complete strangers.

How To Fix An Unsuccessful Cat Introduction - TheCatSite

Unsuccessful cat introduction can lead to stress and conflicts in your furry family. Discover the steps for a proper reintroduction.

thecatsite.com