I'm sure this has been done a million times but I have searched so I'm sorry.
Our cat is 3, we had two of them but lost his sister when she was a kitten.
On Friday we unexpectedly adopted another cat, another neutered male, but I think about 8-9 months old.
Original cat is fine, he just looks at cat 2 with lofty disinterest. However, new cat hisses and spits and has tried to attack cat 1, to the point where he frightened original cat who is normally so laid back he's horizontal.
We're now keeping them apart, new cat is absolutely fine as long as he doesn't see cat 1. He's happy to sit in places that must smell of cat 1, he just can't stand the sight of him (even through the window).
Anyone got any tips? Thanks 