How to stop my cats from being aggressive and hissing at my baby?

Unfortunately, kittens that were bottle fed can be aggressive and not as friendly. You can try to put some feliway diffusers in the House and spray her sleeping areas. Feliway is a cat pheromone which can sometimes help to calm them. Also, give her more time. She has been moved from multiple house in her short life and now around new cats (they don’t usually remember family). This can be stressful and can take weeks for them to acclimate to. I hope this helps and she starts to get use to her new living conditions.

I would try a Feliway spray, diffuser or collar. It is a pheromone that helps with relaxation and anxiety. There are also supplements for anxiety. Set up separate areas for feeding and two litter boxes so they each have their own space with an area that they both have access to. Usually over time they will adjust if left alone. If she’s still aggressive there are prescription medications to give her for a little while to help her adjust so please discuss this with your veterinarian. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Kaji.

Unfortunately it's going to take time. That said, there are a few things you can make sure of to help reduce stress, especially in a four-cat household (which is a lot!). Making sure each cat has their own space where they can eat, drink, play, observe, etc without the other cats bothering them can help reduce territorial disputes over these items. Pheromone collars and plug-ins (Feliway) can also be placed on stressed out individuals, or in shared rooms (since everyone seems to be stressed) to help reduce inter-cat aggression. Making sure to have at least one litter box per cat will also help reduce stress and competition over them, and reduce the chances of accidents elsewhere. Otherwise, continued slow introduction of the cats is best. If anyone starts to get agitated or too excited, removing them to let everyone calm down and settle back in is best. Continued aggression and upset may also need a trainer or veterinary behaviorist's help. That said, if your home is very small, four cats may just be too much for everyone to get comfortable.

You can consider re-homing him if that is what you would like to do. Your other option is to take him to the vet and speak to them about getting him some behavioral modification medication that he can take daily which will hopefully calm him. You should also try some Feliway diffusers and some environmental enrichment for him. ( https://www.feliway.com/us/Products/FELIWAY-CLASSIC-Diffuser ) ( thedrakecenter.com/materials/environmental-enrichment-indoor-cats ) ( https://www.youtube.com/watch?v=AejmrLa_Cs4 )

Is she biting and scratching you or the other cat? This sounds like something has changed and she is stressed. I strongly suggest you visit this website (Feliway) and purchase some of their products. The website has good cat behavior information and the products are basically "happy cat" pheromones that help to mellow cats out. Of course it won't work for every cat but I have had many respond favorably to this treatment. I like the diffusers that you plug into the wall. https://www.feliway.com/ca_en If this does not help then I suggest you talk to your vet about putting her on medication for behavioral modification like amitryptilene, fluoxetine or other. These work well but it is best to try something natural like the pheromones first. Hope this helps. Best wishes.

I suggest you use some Feliway diffusers in the house and also do some environmental enrichment. Feliway really works wonders at reducing stress and calming cats. ( https://www.feliway.com/us ) ( https://www.allivet.com/p-1865-feliway-diffuser-plug-in-starter-kit-for-cats.aspx ) Environmental Enrichment resources: ( catbehaviorassociates.com/what-is-environmental-enrichment-and-why-does-your-cat-need-it/ ) ( youtube.com/results?search_query=environmental+enrichment+cat ) Hope this helps. Best wishes.

Here is a great article on introducing a new cat to the household. https://www.petcoach.co/article/5-steps-to-introducing-your-cat-to-a-new-feline/ You might want to back up a few steps and try to start the introduction over from the beginning. The second thing you can try is to help Fiona deal with the anxiety of the new kitten by using Feliway, which is a cat pheromone that can be calming. It is available in a diffuser that is plugged into an outlet and is great for a room in the home. It is also available as a spray, which can be used on towels, or the most common locations Fiona likes to spend time. https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=8906 https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=37241 Another product I like is Composure, which is available as a little treat. https://www.petco.com/shop/en/petcostore/product/vetri-science-composure-feline-bite-sized-chews If these do not help, you might consider discussing prescription medication for anxiety with your veterinarian. Thanks for using PetCoach.