Cats can become jealous when they feel that their territory is being invaded. Jealousy may occur when a cat witnesses another cat, other animal, or human is getting more attention from the owner. This jealousy may change depending on the type of "cat's personality and temper." The cat can become insecure due to this jealousy from the lack of bonding, socialization and attention. Aggression and depression of the cat are all possible reactions from this jealousy. If the owner is having a difficult time keeping up with entertaining the feline, toys and play houses may help according to catological.com.
https://www.catological.com/can-cats-get-jealous/