Help: Introducing kitten to kitten

Hi all, I've read the sticky and other similar threads, so I've got some idea of procedure for intro. Unfortunately I started off badly by introducing them face to face briefly, though the interaction wasn't too bad - a lot of sniffing, some tumbling, and the new kitten hissed a bit. Afterwards I put the new kitten in the closet with his stuff, but the gap beneath the door was big enough for them to swat at each other, so I closed off the bedroom door too. When it's closed, the older kitten seems to be content to go about her business. I let the younger kitten free in the bedroom when the door is closed, then shut it in the closet when I bring the older kitten in for some interaction. Then I open the closet door a crack and they swat at each other, sticking their paws under/around the door/etc., but it doesn't seem harmful, and there is no hissing/growling. Today during these interactions I was giving them treats too.

So tonight I let them out in the bedroom together. At first they were sniffing, then some chasing and pouncing, but no hissing. I broke them up when they started to fight. The younger one didn't seem frightened at first, even coming after the older one, but eventually the rumbles got rougher, and the younger one started hissing and looked frightened, trying to run away, so I separated them again.

I was reading somewhere else that it is best not to break up the fights unless it gets really serious because then the dominant cat doesn't have the opportunity to assert its dominance and so each new battle they start from scratch and get more violent each time to get the message across!! I also JUST read that once you introduce them, you shouldn't separate them again, is this true?!?

So...am I going too fast with this? A lot of the posts are saying days/weeks of separation, but they seem to be based on old CAT, new kitten, but our kittens aren't really doing all the hissing/growling stuff, so it seems like they're skipping the first stage. The older kitten has been with us since mid-September and she's 5 months. The younger one is 12 weeks and we bought him yesterday. I'm so scared to leave them to fight it out. The little guy looks so small and helpless compared to the other one (even though she's small for her age!).

So I guess what I'm asking is: what should I do next? Should I start from scratch, keeping them separated, doing the scent exchange (which I have been doing really anyways since they can smell each other on my clothing and in the bedroom), etc., or should I let them scrap it out? And if I let them fight, should I separate them again after?? How about if the fighting gets bad??

Thank you so much for the advise!!!!!!!!!!!

It is recommended to introduce kittens within 4-5 months and younger and/or cats 15 months and older, spayed/neutered. This because the "teen" period is when they go through the peek acceleration of development and hormonal change.
Are you sure there aggressive interactions are negative? Do they actually attack and destroy one another or could it be sibbling social interaction?

Are both of them spayed/neutered? Sounds like it was a little bad at first, but better now. I'd just let them together and not separate them anymore. Clip all nails and only break it up if they really get into it.

Charlie was 4 months old when we got him; Ling was a little over a year (they are approximately a year apart in age). As he grew, he would challange her more and more and they really would get into some heated battles. Our lab would break up more fights between them!

They still will challange (both want to be top cat) and we just clap our hands and yell "ok guys cut it out, break it up" and they stop.

Yours are younger and they will adjust a lot quicker to each other.

Clip the claws and let them interact as much as you can. The problem is with the word "kitten." If you're talking less than 4 months or so, they should adapt very quickly. Older than that may take a while. Some have said as much as 3 months for full integration.

The older one is 5 months, younger one is 12 weeks/3 months.

The 12 week old isn't neutered yet. The older one was spayed already when we adopted her. I don't know how negative the aggression was. When they were just pawing at each other through the door, it seemed almost playful, and the first few tumbles seemed gentle enough, but then the older one looked like she was biting a bit and the younger one was hissing a bit (though there were no scratches or blood).

Originally Posted by bbleho

The 12 week old isn't neutered yet. The older one was spayed already when we adopted her. I don't know how negative the aggression was. When they were just pawing at each other through the door, it seemed almost playful, and the first few tumbles seemed gentle enough, but then the older one looked like she was biting a bit and the younger one was hissing a bit (though there were no scratches or blood).

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That doesn't sound like real fighting to me. That sounds like the way kitties play and wrestle. They do "bite" each other, but it's more like the kitty biting your hand in play -- not chomping down. The hissing is the other cat saying, "stop it, that's too rough".

If there were real fighting, you'd be hearing blood-curdling "yeows".

Honestly, at this point, I would just let them interact and have at it. It may take a day for them to figure out their limits. Just give the little kitty access to his "safe" room if he needs a break.

Thanks everyone for the responses. I let them go at it, they were tumbling around for a while under supervision, and it was safe enough, so I lightened the supervision (we're in a condo, so it's easy to keep an eye on them). I also fed them together and they were eating out of each other's bowls. I'm not sure who's winning the dominance war at this point!! The little guy is a stickler! He finally tired out and the older one was playing with some toys in the room and finally went to nap in her bed in the other room - which is good because I was about to separate them again to let them rest. Hopefully they'll sort things out between themselves soon and we can all be friends

I'm sure if they are like most kittens, the dominate position will change many times Cats usually do not keep the position their entire lives. Its more loosely based - unlike the dog pack which has stronger positions for most of the dog's life.

Hey all, just wanted to update: looks like the kittens are friends now, though I think Banjo (the younger one) gets on Sasha's nerves with his non-stop play! A few times we've cheered her on when she "takes him out" (gently of course) because he drives us batty too heehee. They were curled up in their bed together today, and they both slept with us last night. We're a happy family again! Thanks everyone for helping me out