The reason why, in general, domestic cats find it hard to live closely with other cats is because emotions relating to interpersonal relationships are quite possibly beyond their abilities (note: cat emotions are being discussed). I have argued that cats can be jealous. This does not mean that domestic cats can’t be sociable. They can and often form friendships. But they also often simply tolerate each other in multi-cat households.
As the cat’s domestication is progressing and as therefore there is a greater need for the domestic cat to be a social animal, the cat is currently sadly ill-equipped for the demands of the future.
He or will have to learn the emotions designed for interpersonal skills. Is this possible?
P.S. Although cat emotions are probably not as sophisticated as cat owners would like they no doubt possess at least a basic range of emotions shared by all mammals simply because they need them in order to e.g. make good decisions about whether to run away in fear or feel the warmth of their owners lap and the joy of companionship from a human caretaker.