Does my cat want to be an only cat again?

I adopted an 11-week-old kitten a few weeks ago, and had been feeling guilty because she seemed to have so much pent-up energy and sociability when I got home from work. Even after extensive play, if I turned my attention elsewhere she would try to claw her way up onto my lap or pounce on my feet. She was gradually learning not to bite and scratch, but was still a little crazy, so I thought maybe she needed someone to play with while I'm at work. When I found out her little brother, the runt of the litter, still hadn't been adopted, I decided to see if she would be happier with him around.

The folks at the clinic where I got them said there wouldn't be any need for a lengthy re-introduction for recently separated littermates, but she had a different opinion. Yesterday when the little one came home, I let her sniff him in his carrier, and then when he finally came out, she sniffed him some more -- and promptly decided to show him who was boss. It didn't seem like ordinary, cute kitten fights, because she was clearly winning every single one, had him pinned down by the neck, and the poor little guy was squealing in alarm. I set up his own little space in the bathroom and back hall, but when they were calmer, I let them try to get re-acquainted again. More fighting. I ended up separating them for the night, spending some quality time with her in the living room, where she's been sleeping, and then he was sleeping right outside my bedroom so I got up and petted him numerous times in the night and he seemed content.

Today she's less mean, and even once groomed his tail for 30 seconds and later let him lay down next to her. He's been squealing less. But mostly she's been extremely domineering, ostentatiously eating his food, drinking his water and using his litterbox. Woe betide him if he tries to play with a toy -- she's got it away from him instantly and punishes him for his impudence. I tried bringing him into the kitchen to eat, but he went scampering back. He seems to want to make friends. She seems to want to be around him, too, but mainly to keep guard. She watches him like a hawk.

Does this sound like ordinary littermate rivalries that will soon be resolved, or did she get too used to being an only cat already? If she's not going to take to him, I hate for him to get stressed out by all this bullying only to go back to the shelter, and I don't want to get too attached to him if he can't stay.

Thanks for any advice on warring siblings!

the clinic was incorrect, a new introduction would be necessary, even for littermates. They do not remember each other (which is common) and so separating them would be the right move for now. She is clearly Alpha so put her bowl down before his, but feed them in separate rooms until they acclimate to each other.

They will get used to each other again. She just needs time to get used to him again. I would keep working on the introductions.

We had found Oskar a couple days after we found Sage and Jinx and they took a couple hours to get used to Oskar again and they were fine. But that was only a couple days. Sounds like these two have been apart longer than that.

I guess your two must have been apart a lot longer than mine. I adopted the runt of the litter first, and then decided I wanted him to have a companion. Two days later we adopted his sister. Being a cat behavior novice at the time, I didn't even think about the need for reintroduction. We just let her out of the carrier onto the bed and she came and slept on me for a bit. Then we put her in the night time "playpen" we had constructed for the kittens because they were only six weeks old at the time (the owner wanted them out of his house as soon as possible, so we had to take them a little early). They slept together that night, and it seemed to me that they remembered eachother. Maybe that's becaues they were so young or that it was only two days. I was surprised by your post because of the similarity of our situations.

You can barely tell which of my two is the alpha because Cleo eats first when the food is put down, but Alex won't let her play with any of his jingly balls. Alex is the one that hisses and growls at Cleo when they come home from the vet too. Maybe I'm just lucky that they have gotten along so well from the beginning.

It seems to me that you will have to do a slow introduction for these two as if they were adult cats and your girl has been there for years. Keep them separated, with their own food, water and litter. Allow them to smell each other from under the door first. Then after several days you can begin to allow supervised time for them to check each other out in person. Make these visits brief at first, and then increase the intervals of time. It may take several months for you to teach these two to get along. Be patient, and good luck.

Rocket started getting along better with her "new" brother (they'd been apart 3 weeks) by the end of the second full day together, so I just separated them at night to be sure he had some quality time with his food, water and litterbox. I never went through with a reintroduction. I did try the trick of rubbing the same scent on both of them and that seemed to help a little, tho not immediately. I think after they'd been doing so much wrestling, they both probably smelled pretty similar by then, anyhow.

Rocket is still definitely Alpha Cat but she's much kinder -- there's more racing and chasing than fighting and the wrestling now is more WWF than WWII, although she can still make him squeal. I think she likes having someone to boss around. I actually saw them grooming each other briefly -- as soon as I tried to take a picture, they took to wrestling around again. He seems very attached to both of us, if we're both in another room he'll cry a little until I call to him.

Thanks for all the advice!

I am glad they are getting along better. That is great!