I have an 18 y/o male that would hiss and growl if a cat even walked past the house, but I decided to get a second cat who is 11 y/o male. The older cat was standoffish, occasionally hissed and hid a lot, for about a month. The new cat wanted to make friends and pushed for contact from day one. Now 5 months later, they groom each other, sleep next to each other (no cuddling, however) and share a litter box. One thing they will NOT do is share a food dish. So get a second cat of about the same age and do a slow introduction. Keep in mind that a kitten is very active and will sometimes just irritate an older cat. And that causes fighting. Good luck and chose wisely.