This is easier for them to do if they have grown up with the other cats as although unrelated, they are perceived as belonging to the same social group. As cats in the wild tend to live and hunt alone, having to suddenly share resources with another feline, can create stress in either cat. It is often a mistaken conception that cats need another feline companion. Often what they do require is a changing, interesting environment, with access to the outdoors, and games with their human caregiver. If access to the outside is too dangerous as homes are on a busy main road or other dangers, then enclosing entire gardens can still provide with important access to vital enrichment such as trees, plants, bushes, and the opportunity to hide in bushes sunbathe and go high to survey the surroundings.
Advice by Vicky Alhadeff BA, DipSMP, DipCAPBT, TTouch P1, IMDT, a companion animal behaviourist and Tellington TTouch practitioner. http://happydogsandcats.co.uk/