Kitten lost his brother, is in isolation and miserable

I took 2 stray kittens in when they were 3 weeks old, they are now almost 9 weeks old...well, one of them is. Every thing was going very well with them and they have been a pleasure. However, very suddenly and unexpectedly, I lost one of them to sever pneumonia this past Tuesday...he passed on at the hospital. Even being in an oxygen tank for 2 days could not help my little guy. Both of them got sick, it wasn't the one that died who got sick first or worse...that's why it was very unexpected. The other kitten has recuperated and is doing wonderfully so far, he gets his first vaccine next week.
They both had been tested negative and were out with the rest of my cats for a week before they got sick, since then, I've had them locked in my bedroom. They hated not being with the other cats, but atleast they had eachother. Now, the one kitten is all by himself and he's undergone a complete personality change. He doesn't seem to be depressed by his brother's absence, if anything, he's been alot sweeter now. But without companionship of the other cats, he gets really wired up and hyper by himself...he was not at all this active when he had his brother to play with, and he just seems lonely.
I've been told to keep him separated from the rest of the cats until a week after his vaccine...this will be almost 3 weeks that the poor guy will be in isolation by himself. He tries so hard to sneak out of the room and I know he's miserable by himself. Obviously, I try to spend more time with him but I still feel bad. I hope he doesn't think I'm punishing him, I just want to take precautions so he doesn't get sick again.
Is this going to have any psychological impact on him?

It has been my experience that they snap back pretty quickly. When Fred lost his best buddies, both times he seemed depressed and clingy for awhile, but after awhile, he was ok. Kittens seem to do a little better. I think he will be ok once he can get out and socialize. Sorry about the loss of the little one.

Buy him a cat condo, put it in your bedroom and buy him a snugglekittie, this will help him while he is in isolation. Play classical music really low for him in the room. Any music with harps in it really calms them down quickly.

Agree with Hissy's advice - your baby needs stimulation and a snugglemate, even if it is a snugglekitty. We had a similar situation just recently, and when the kittens came out of a 30 day quarantine, they acted like nothing had happened. They were back to normal with the older cats the moment they were free. Kittens are very resilient that way. And of course, like you are doing, we spent as much time as possible with them while they were separated.

Hang in there....you are almost thru this!!