Cats are generally solitary creatures. However if you don’t know their natural behavior, you can cause them unnecessary stress. For example, cats like their alone time. While some cats enjoy the company of others, others prefer to have their privacy, even among other cats.
Cats also don’t like sharing litter boxes so the general rule of thumb is to have one more litter box than you have cats. After following so many rules to keep your cat happy, chances are good you’ll be broke, unhappy, and a virtual prisoner in your own house, but as long as your cats are happy, that’s all that matters anyways.