Cats can be possessive and territorial animals.
If cats are brought home together as kittens, they usually get used to each other quickly and rarely have a problem getting along. However, if you have a houseful of adult cats who all get along and they try to bring a new kitten home for the first time, trouble can start brimming. The kitten, however may not be at all bothered by the adult cats and may even try to play with them, only to get batted at, hissed at, and in circumstances where the adult cats are not declawed, scratched. It may be a good idea to get your adult cats declawed before bringing home a new kitten. This will help the adult cats get to know the kitten's smell.