One of the reasons I got my kitten Alibi years ago was so that my cat Keyser could have a friend and playmate.
It appears though that I didn't check with Keyser about that because she apparently didn't want a friend and playmate.
Since the day the two came together they tolerate each other at best and sometimes hiss and spit.
They don't curl up together, they don't clean each other, they don't chase each other for fun.
Once their noses touched over the water bowl but that is it.
And yet over the years I see other friends and family members whose pets become close and are very sweet with each other. That is never to be for Keyser and Alibi.
Not sure what I did wrong. They are both female. Keyser was older but only by a year or so. I didn't think she would be that set in her ways.
I once asked a veterinarian about it and he suggested to new owners trying to merge new cats together that they turn down the heat in the house (or turn up the air significantly) so that it is bone-chillingly cold. Then the cats will gravitate to each other for heat.
Wish I knew that then.