Jack and Booter got in a fight :-(

I have a neutered cat named Jack that I adopted as a kitten. He is 2. He is a very laid back kitty. He's been raised with 2 children and a Chihuahua.

About 6 months ago my boyfriend's long time friend and neighbor passed away. My boyfriend took the man's four indoor cats. We thought we'd try one here because Jack's not a lap kitty. 

Booter was very shy at first but he soon accepted me, then both kids. He and Jack gave each other wide berth for a long time but recently I felt like they were playfully chasing each other. Booter doesn't like the dog, but he's not terrified of him. When the dog is penned up in my small galley kitchen Booter often goes near the gate and then hisses when the dog approaches. As far as I know, Booter is a neutered male.

Two weeks ago I took in a pregnant stray. Just a few days later she had 3 kittens under my bed. Jack and Booter both try to go in my bedroom each day, but we don't allow it.

Tonight, Jack and Booter got in what I think was a real fight. Booter was definitely the aggressor though Jack outweighs him. Booter has spent years as a stray and has lived with other cats his whole life. He was being bullied by one of the other 3 when he was at my BF's house.

I'm wondering if having the mama and her babies in the apartment is throwing everyone off. I think I may have petted Jack after I petted the mama without washing my hands (I'm usually pretty compulsive about hand-washing). 

I don't know what to do. I broke up the fight by squirting Booter, then I put Jack up on one of our cat shelves. Booter tried to go after him so I squirted him and then my DD10 took Jack with her when she went to bed.

I'm worried that they'll fight after I go to bed.

It does sound like redirected aggression. How are Jack and Booter doing now?

It is usual to separate the cats when they have an all out, no holds barred fight for awhile to let them both calm down. After a couple of hours you could then open the door a crack and see how they react to each other. If you just let them alone their relationship with each other may deteriorate. 

I think you are right, they are stressed by the new cats on their territory and are taking it out on each other. The rest depends on what you plan to do with the mother cat and / or her kittens. If you have a large house you could block that part of the house off and try products for stress ie feliway, calming chews, etc until the kittens are old enough to either leave their mother or to integrate with your current household of cats. 

Thank you for your reply and suggestions. They've had one more fight since my initial post, but it was shorter than the other two. Jack is staying with a friend for the next two weeks (so is the dog) so they'll both get a break.

Don't be surprised if the problem isn't automatically fixed. I really do suggest you separate them when they come back together in the one house and reintroduce them gradually.