Since cats are territorial creatures, bringing a new cat into your home can be problematic. The best scenario is to get two cats at the same time so that neither is infringing on the other’s territory. But what if you already have a cat?
When a kitten is introduced to the house of an older cat, you need to make sure not to neglect the older cat. This is extremely easy to forget when you’ve got a new kitten as people tend to fuss over kitten a lot more than older cats. The older cat may become jealous and start fighting with the new member of the family. This can lead to other cat behavior problems where a cat might decide to start urinating outside of the litter box, or it might stop eating and get sick.
If conflict arises, try to keep the cats apart for a time until they become used to one another. You can put their litter boxes in different areas of the house and keep the food dishes apart. Any time that one shows aggression to the other, calmly step in and prevent the battle from escalating.
By considering the feelings of the older cat, not neglecting it, giving it sufficient time and letting it know that it is still special, there is a better chance that the new kitten will be accepted by the established cat.