First of all, I really want to compliment you on your attitude about this. At TCS we encourage people to understand that "animals are for life," like children.
The only problem is at some point children become easier to communicate with - and communicating with our kitties takes (seemingly) more work. It's just a matter of figuring out how to talk to them in a language they understand.
I don't know how you handled the separation, but just simply separating them for a time won't do the trick. This needs to be treated like a new introduction, and there's a lot more to it than just separating them.
Are you willing to keep them in separate rooms for a minimum of several weeks - up to several months? Can you and hubby give each one the attention they'll need while they're confined? Are you willing to add a screen door (or replace the doors with screen doors temporarily) of the "separation rooms" ? (During this reintroduction period).
If the answer to all these questions is yes, then you're good to go.
Firstly, here's an article that will help. It's written for an introduction that involves a resident cat, but the ideas are the same: http://www.thecatsite.com/Behavior/4...cing-Cats.html
The basic idea is to get each cat to associate the other one with good things. Then to SLOWLY reintroduce them to each other - in the meantime, you and hubby are bonding with the kitties on a positive basis.
You also need to diffuse the stress and tension in your home. There are three things that may help. One is the separation and lots of time with you and hubby with each kitty individually. If you sew, read, fold laundry, work on a laptop, iron clothes - do these things in one of the kitty's rooms. Maybe move the TV into one of the rooms for one week, and sit in there to watch TV. Change rooms the next week. We need to avoid the kittyies becoming bored or depressed during this adjustment period.
Buy bird feeders with suction cups, attach them to the windows. Squirrels and birds are great "Cat TV" and will provide hours of entertainment.
To further help destress the environment, if you can afford it I'd consider purchasing Feliway diffusers (the plug-ins). Less expensive (and just as effective if you keep the spraying up) is the Feliway spray. Feliway is a synthetic hormone that mimics the friendly markers in cats' cheeks. Also, I'd consider Flower Essences. Some cats respond really well to these - others don't. Again, if you can afford it, it's worth a try. Both Feliway and Calming Flower Essences can be purchased here: http://www.catfaeries.com
OK. Now to the reintroductions. Because neither cat is resident, I'd seriously consider adding screen doors to the separation rooms if possible. If not, consider replacing the doors temporarily with screen doors. There's a way to manage it if that's not possible, but it's easiest given that this will likely take some time. You have to undo basically four months of aggression.
Take a few rags, wash clothes or towels - whatever (preferable washed without scented fabric softener), and rub each kitty all over with a couple of small towels. Put kitty A's "scented towel" under kitty B's food dish, and vice versa. Then in the morning or evening (or both), or especially after a good play session, put treats out for kitty A on another towel that smells like Kitty B (and vice versa).
This will help them come to associate good things with the other's smell. Cats learn well by positive association - and right now they just associate each other as rivals.
Do this for at least a week. I'd probably give it two.
IF you do the screen doors, then you can let one kitty out at a time to hang out in the house. I'd even consider letting Kitty A out for one day, and letting Kitty B out the next day. This will help them get used to each other's smell around the house - but without the association of being attacked. This works if you've added the screen doors - that way you can close the regular door while one kitty is out in the house (at first) - because any interaction through the screen door must be supervised. And again - I'd give total separation at least a week - and maybe two.
If you replace doors with screen doors so can't close the door, then no kitty should be released all day - only when you can supervise any potential interaction through the screen door.
Hissing through the screen door is OK - but if ears go back, backs get ridged - then gently remove the not confined kitty and take her back to the separation room without saying anything. If they just sniff at each other &etc., just let it happen. ANY "good" interaction between the two should result in praising them to high heaven. "What GOOD kitties!" "Such good girls" &etc.
Meanwhile, keep up the scent-swapping. If they react to catnip yet (which they probably don't), get two catnip toys. Let each one drool and rub all over it. Give it a week - then swap the toys. (Cats get used to catnip, so after having it out for a day it needs to be removed for at least a week to be "effective" again).
When you get interaction between them through the screen door where kitties are curious or interested and not aggressive - give it a few more days. Then you can begin supervised direct interaction. I'd give it no more than 10 - 15 minutes at first.
Through all of this, make sure that the kitties understand they are not being punished. They're not bad kitties - you're just helping redirect the stress and aggression they've been experiencing.
Also, if the first time they interact between the screen door it's back to both expressing major aggression, separate them again for at least a week, and continue the scent swapping. Also, keep an empty can with coins in it handy - and if they start snarling and growling at each other with really agitated tails, ears back - or actually go at the screen door - shake that can LOUDLY. The loud noise will startle them out of the attack. Then pick up the kitty not confined, and carry her back to "her" room.
So... all of this has been predicated on the use of screen doors. If you can't do this, the principles are the same. Let one kitty out one day, the other kitty out the next day. They'll be able to smell each other under the door. Just watch what happens. If the not confined kitty growels - take her back to her separation room.
Again - keep them totally separated at least a week (or two). If there's no negative response to the smell under the door, get a child gate and put it in the door frame. The problem with this is that these kitties can easily jump over it, so when you're ready for the initial reintroduction, one of you must be in the room with the kitty, and one of you must be outside the door.
But the idea is to let them initiall just be able to smell each other (closed door). Then let them see and smell each other (screen door or child gate) - supervised. If after a few days of seeing and smelling each other without any negative response (with kitties being praised to high heaven for lack of signs of aggression while smellling or seeing each other), then you move to the letting one in the room for a supervised visit for 10 - 15 minutes. Again - no negative response to each other? Praise them to high heaven.
Switch rooms each day - one goes into the other's room. After a few days, if there's no negative interaction, begin to lengthen the time they spend together. Make it half an hour. Then an hour. When they can spend two hours together, then try letting them out into the house (after a couple of days of spending several hours together with no negative interaction).
This will take a minimum of two weeks. I'd give it a month, personally - depending on how kitties react. The slower you go, the more likely you are to have success.
Remember - some hissing or swatting is normal. They do still have to decide which one is going to be alpha. And if there is an attack once they're out (if you get to that point) - keep that can of coins handy to startle them out of the attack. Don't ever physically get inbetween them while they're fighting.
I hope these ideas help, and any questions you have - if you decide to do this, PLEASE feel free to ask!!!!!!!!!!!!!!!!!!!
- and thank you for wanting to make it work for the kitties!
OH - PS. Separating them should help stop the aggression against you. But if you want to help them along, you can each also get a t-shirt really good and sweaty, and at some point, once a day, instead of putting the other kitty's scent towel out with treats, put out treats on one of the smelly t-shirts.
Also - if either kitty is showing signs of aggression to you while separated, simply leave the room. They need to learn that inappropriate behavior does not get them attention. And if they don't show aggression towards you, spend as much time in each room as you can. Some of that time should be doing something else, so kitties learn that you are there and have a life, and are not solely focused on them. Ignoring cats is a GREAT way to get them curious about you and to feel safe around you.