tommy doesn't like his little sister

here's the story...
my sister brought home two cats from the SPCA, where she works. tommy came first, then a couple months later came drew. tommy is about 5 months old and is fixed. drew is about 3 months old and not fixed yet. drew also has Cerebellar Hypoplasia [but she's getting stronger and adjusting well]. tommy goes everywhere in the house, but drew currently lives in her own room that my parents made into a big play-pen for her [we take her out often and play with her a lot]. they want to move her downstairs but tommy plays VERY rough with her. i understand that they are technically still kittens, and kittens love to play-fight, but she just can't defend herself very well. tommy goes for her neck and she screams. :(
what i'm wondering is---will they ever be able to live together peacefully? i know tommy is pretty upset that our attention goes to drew as well as him now.

Humm,

Once Drew is fixed, I'm sure Tommy will lose interest. She is an intact female and is probably putting out all sorts of scents that are making Drew act like he's doing. I think it's best that Drew be kept in her own room, at least for her own safety.

It's not always a male/female thing either. It's just plain a hormonal thing I think. We had Pooky & Bear neutered at 5 1/2 months old (which is about 1 1/2 months earlier than the vet prefers) because they started getting aggressive with each other and the other cats. Even though both male and brothers to boot, hormones seem to override relationship.

I think once things are healed up from the neuter you should start seeing your kittes learning to get along again. If not consult your vet in case there is something else going on.

hey thanks you guys!
i appreciate it. drew should be getting fixed soon. i hope it all works out and they become friends [or at least stop trying to maul each other]. :)