Why are my sister cats fighting after one had kittens? How to stop it?

I hope these two cats are not related. Breeding related cats is NOT recommended. It sounds like he is trying to get her pregnant again and she doesn't want him. You cannot force cats to get along. They may never go back to the way they were. It is best to spay Mella so that he stops trying to breed with her.

She’s probably coming into heat again and that’s why he’s after her. I recommend spaying her when the kittens are weaned. Once she’s no longer cycling this behavior should improve. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for your cats.

Changes in the social structure in a household like this can be very stressful for cats. They are not a very social species by nature, and it's often very hard for them to accept "newcomers" - even if these are her sister's kittens. I would recommend making sure that the aggressive cat has her own area where she can get away completely from the kittens and your other cat whenever she wants to - this should be a comfortable room with a litter box, food and water bowls, a cat tree or other resting spot, etc. This way, she can be on her own if she prefers to, but can still come out an interact with the other cat and her kittens if she chooses. Feliway diffusers in the areas where she spends most of her time may also help to reduce her stress. It may take her weeks, months, or even longer to adjust, so be patient - some cats never really adjust, unfortunately, and may need to be kept in separate areas of the house to keep everyone happy.

I am sorry to hear about your kitties! It is possible there is a change in dynamics if one cat has now reached sexual maturity. If he is not already neutered this may help. You can also get a Feliway multicat diffuser for your house which can help reduce intercat aggression, but it may also take some time and training to get them to get along again. You can read about methods for training the cats to get along again at https://drsophiayin.com/blog/entry/feuding_felines/

This sounds like a very frustrating issue! It is difficult to determine why Chino and her friend are suddenly having so many issues. At this point, the best thing you can do is get both cats spayed to remove hormonal influences that may be contributing to their aggression with one another. You can also use calming pheromone collars or diffusers (Feliway is one brand) for both cats. If the aggression continues after those options, it may be worth consulting a veterinary behaviorist to evaluate their behavior in your home. Keep both cats separated unless you are directly supervising them and avoid putting any part of your body between them if they fight. If they do begin to fight, dump water on them to distract from the situation and separate cats immediately. I hope that all goes well!

You may need to make some adjustments so you can help keep your home a low stress and comfortable place for your cats and get Piper and your other cat to get along. Cats need at least one litterbox per cat plus one extra to help reduce stress associated with the litterbox. They should be placed in separate rooms, away from the food and water bowls, must be scooped at least daily (preferably multiple times a day)and washed out at least weekly with a mild soap, followed by thorough rinsing. Cats need a lot of space to explore, but keeping them indoors is much safer than letting them outside, due to the risk of injury from cars, wildlife, other animals, etc. The key is providing space (particularly vertical space for climbing, such as cat trees, ledges, and the like) inside the home. Visit veterinarypartner.com and healthcareforpets.com for tips on stress reduction. The following link has information on introducing a cat to your home: https://indoorpet.osu.edu/cats/felinelifestressors/new-pets Also look into Feliway, a synthetic pheromone that is available in a diffuser and spray form that promotes calm feelings in cats http://www.feliway.com , and feliway friends, which is a pheromone that can help cats get along with each other better https://www.feliway.com/ca_en/Products/FELIWAY-FRIENDS-Diffuser I highly recommend you have Piper spayed, as sometimes the hormones associated with not being spayed can worsen behavioural issues. Spaying also stops the heat cycle, eliminates the risk and cost of unwanted breeding, and can reduce the risk of uterine and ovarian cancer, as well as reduce the risk of potentially fatal uterine infections and breast cancer. Good luck, and I hope your kitties start to be friends soon!

Hello. Unfortunately, this is not a friendly family group. Cats do not often form strong bonds with their offspring & she may be feeling a little threatened by having them around as they get older. It may be a good idea to either find homes for the kittens, or consider spaying the mother cat. This may alleviate some of her anxiety. Hopefully, things will even out for her soon. Thanks for contacting Petco Pet Education Center, formerly Petcoach.