My boyfriend and I took in a kitten (about 5 months old) 1 month ago. A spayed female we named Lily. We already had 2 adult cats, a neutered male named Indy and another spayed female named Salem. Indy and Salem are both 4 years old. We hadn't planned on having a 3rd cat but we found Lily abandoned and decided to take her in.
Indy and Salem are both very loving and so is Lily. When we had just Indy and Salem, they almost never fought and barely play fought but would sleep together and seemed to enjoy each others company.
The problem is Indy and Lily fight or play fight several times a day. I read that play fighting usually involves little noise. I've watched them for hours to figure out what is exactly going on between them and often Lily will roll on her back and let out a bunch of little meows which gets Indy's attention. He comes over and they kick and bite each other with some meows here and there. After a while, Lily will growl when Indy is biting her so I'll break them up. Lily hisses and bats her paw at Indy and then rolls on her back and the whole thing starts all over again. I've seen Indy and Lily start things and there doesn't seem to be one who is always bothering the other, but when things start Indy gets full of energy and loves to chase both girls around the house. If he catches Lily he pins her down and she cries so I break them up. Again, right after they're broken up Lily goes right back to Indy. I have noticed that Indy likes to bite Lily on her neck but there is never any blood, scratches, or bite marks on anyone.
When the two are not fighting or play fighting they get along fine. Indy and Lily will bathe each other and purr and sleep by each other. Salem gets along well with everyone.
The growling, hissing, and loud meowing worry my boyfriend especially and he is worried we will have to get rid of one of the cats. I've never owned a kitten before, or dealt with cat fighting or play fighting. Prior to living with me, my boyfriend has never owned a cat but loves them like children and would hate to part with any of them. I'm not sure what to do to monitor their behavior. Any help would be appreciated.