Will my two male cat brothers fight or get territorial as they grow?

Whether they fight or not is going to depend on a lot of factors including how well they get along, their individual personalities, and if there are cats going into heat near them which could lead to competition. Three months is a bit young to be sexually active so they likely won't fight (if at all) until they are older, and you still have time to get them neutered. Looking to see if there is a low-cost or no-cost clinic in your area that you qualify for may also help with getting them neutered sooner.

They may always be enemies but there are a few things you can try to help calm them. I would start by putting some feliway diffusers throughout the house. They have a multicat version now. Feliway is a feline pheromone which is helpful to calm cats. It doesn't work on all. You could also consider putting some essential oils throughout the house. Be sure to get ones that are safe for cats. Visit oilyvet.com for more information. Also, make sure you have at least 3 litterboxes throughout the house, if possible, to prevent competition. If all this fails, you could talk to your vet about putting one (the instigator) or both on an antianxiety medicine to help calm them. I hope this helps!

I would recommend getting them neutered as soon as possible. As they have gotten older they are becoming more aggressive and controlling of there territory. I would recommend neuter, increase number litter boxes, increase food and water dishes to start. Hopefully once all the added hormones are gone they will settle down

Both of them are really cute! I would get the male neutered once his turns 5 months to prevent this behavior from getting worse. The female could go into heat at anytime so I would advise to get her spayed as well. This behavior may never go completely away as it is their personalities. You may try to put some feliway diffusers throughout the house to help calm them. Feliway is a cat pheromone that doesn't work on all but can help with this behavior. They even have a multicat household version now. I would always meal feed and feed them separately as food aggression is really hard to control. I would also make sure you have at least 2, preferably 3, litterboxes to decrease competition. If the feliway and neutering doesn't help, I would talk to your vet about giving the more dominant one something to help mellow him out like an antianxiety medicine. Hopefully this is just a behavior he has since he is young and boisterous and he will grow out of it. I hope this helps!

They are adorable. Yes I would get both spayed and neutered soon. Most cats once they are neutered usually get along better. The longer this aggression goes on though will make the transition harder. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for your cats.

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/

It can take several weeks for testosterone levels to decrease after neutering. Until then, consider using a pheromone product, such as Feliway spray or plug in diffuser, to decrease any anxiety or aggression in the home. Provide extra litter boxes, bowls, toys and bedding to prevent food aggression or resource protection.