How To Go About This?

[Graceful-Lily]

So, as some of you may know, I have a third cat now. And the dynamic has been unusual since he came. There are three cats in this scenario.
First of all, Felix is more lenient with Harvey (the new addition). More than any other cat that has ever been in this house at the same time as him. From their initial encounter, there was some uncertainty from both of them but it seems like once they picked up on each other's scent, they calmed down almost immediately. The do not stare at each other, they do not growl, there is no hissing either. They are able to stand within inches of each other without either of them reacting in any sort of way. There has always been attempts to play with each other on both their parts but it has ended in running away or slapping. Again, when this happens, there is no hissing, no growling, no staring. It's almost as if they don't know how to be around each other. I've also heard them "talk" to each other. I've heard Felix use vocals I've never heard him say in the almost 10 years I've had him. I think it would also be important to note that Harvey was here previously 4 years ago as a kitten. I don't remember the duration of his stay before he was adopted but he interacted with Felix frequently and was pretty attached to him. Throughout those 4 years of him not being here, we would visit him often and I guess we also carried his scent when we returned home. With regard to Felix and Harvey, I'm not sure what this all means since I've never had this happen before. I'm hoping someone with more experience will be able to understand what is going on here.

The second interaction is between Felix and Fayola. They do not get along at all but they tolerate each other. They fight often and I try to keep them separated as much as possible. They were introduced slowly over a period of 2+ months before they started being in the same space. I did a lot of scent swapping, feeding behind doors, short interactions and all but they still don't live in harmony. Adding Harvey to the mix has made Fayola more on edge and she is cold towards me. Things have improved slightly but she will growl and hiss at the sight of either cat. I can't pick her up like I used to, I can't cut her nails like I used to, she doesn't want much to do with me other than a brief head scratch.

Third scenario is between Harvey and Fayola. I haven't started introducing them yet but Fayola has made it very clear that she doesn't like either cat and would prefer to be on her own.

Should I remove Fayola entirely and put her in an isolated part of the house?

 

[Caspers Human]

I say to make sure that each cat has their own litter box, a safe place to retreat to which they can call their own then leave well enough alone.

You should also make sure that there is enough vertical space like cat trees, window ledges and shelves for cats to climb on. Provide a scratching post (or safe place to scratch) for each one, too.

It’s all about territory and making sure that each cat can carve out their own slice of home turf.

Beyond that, don’t do anything out of the ordinary unless there is fighting.

Just let the cats work out their relationships on their own terms.

 

[Graceful-Lily]

What am I supposed to do if they are fighting then? Felix and Fayola are fighting...

 

[Caspers Human]

It's hard because humans don't speak Cat and cats don't speak Human.
But what it comes down to is "cat politics."

Cats have a way of communicating with each other in ways besides vocally or by fighting. Just one cat making a simple change in posture or giving a swish of the tail might mean something to another cat. It's pretty complex. Even long-time cat lovers sometimes don't pick up on all the signals. Rest assured, there ARE signals.

Cats will signal each other to communicate dominance over territory, food, litter box and other things. They need to have time to send and receive those signals so that they can work out their relationships over who gets what territory and when.

If a human steps in too soon, the cats can't communicate and establish good relationships and it will take longer for them to settle down and behave. On the other hand, if the human doesn't step in when it's necessary, cats might not learn the rules of good behavior and that could lead to bullying, territorial squabbles or, even worse, litter box issues.

Like I said, the first thing to do is to make sure that every can can have their own territory that they can call "Home Base." One cat might like to hide under the bed. Another might like to go behind the sofa. The third might prefer to hang out in a closet. I think you get the picture.
Those territories should be the place where each cat can retreat whenever they feel threatened by another cat or even when they just feel like going there to hang out. Remember that, in the wild, cats can be both predator and prey at the same time. Cats might eat birds and mice but coyotes and hawks can also eat cats. This puts wild cats on a proverbial tight rope for survival. Even though house cats are domesticated and don't necessarily need to worry about predators, the instinct is still there. It's hard-wired in. That means that even the sweetest house cat needs to feel safe and have a place where it can go if it feels threatened.

Now, you've got three cats in the same house, all vying for the same territory and each one needs their own safe spot.

Second thing is vertical space. Think "Lion King." Imagine Mufasa and Simba sitting on top of Pride Rock, looking over their territory.

"Look, Simba! One day, everything that the light touches will be yours!"

That's "Cat Psychology" in a nutshell. A cat needs to get up high and survey its kingdom just like The Lion King. Make sure that there are enough places where cats can make their own, little "Pride Rock."

The third part is the hardest... When cats scuffle, how do you know whether to step in? Well... That's where the rubber meets the road. If you step in too soon, cats can't work things out among themselves. If you don't step in soon enough, cats can get hurt or start bullying.

Basically, you set the limit. Decide when enough is enough and enforce that limit. Let's say, for instance, you set your limit at biting. Growling, hissing or chasing might be okay but biting isn't. If cats go beyond your limit, give them one verbal warning. ("No Bites!") If they don't listen then step in and separate them. If they still don't behave, send them to their own safe rooms for fifteen minutes. Both, not just one. Think just like you're giving a two year old kid a "time out." It's pretty much the same thing. You can think of many cats as having the emotional state of a kid in the "Terrible Twos" and you will probably be pretty close to the mark.

If they STILL don't learn to get along then they need to be separated, long term, and start the introduction process all over again.
That's a bridge a bridge to cross when the water goes under it...

If you start with those three things, Territory/Safety, Vertical Space then Rules of Behavior, you should be able to just stand back with a watchful eye and lets your cats work out their politics on their own.