I have two cats, about 1.5 years old and supposed to be brothers, but don't know if that's true =)
My mom also has a cat, she is about 8 years old, a bit crusty and was the only cat in the household since she lives there with my mum.
I tried to bring them with me when I visited her, so that they can play with each other and all that stuff. But my mum's cat really seems to dislike the idea of the presence of other cats. She hisses and snaps at them, tries to hit them and mostly go out of their way and hides somewhere until they are gone.
I have to say, although I got the two cats way to early from the owner, because she lied about the age, and I am not the most talented one in raising cats, they behave really well when we visit the other cat. They know that there is something wrong, but they aren't intimidated by her. They bow down before her, go out of her way, approach very slowly to show her that they mean no harm, so I don't think they can do any better.
We also tried to have them together for a longer period of time, e.g. nearly two weeks when I visited my mum for the Christmas holiday. But nothing's changed.
Is there any way we could improve their relationship? I know, it's the same with people, sometimes you definitely don't like someone. But it would be nice if they would get along fine. That way we could give them to someone together when we want to go for holiday or visit relatives or something like that. Do you have any idea?