I have found that as long as my 11 year old rescue, who happens to ALSO be my most "neurotic" cat feels he is getting all the attention he WANTS from me, and is allowed some time on the screened porch, each evening away from the "rambunctious" Bengal youngsters -- he is FINE with the fact the others are there.
He GRUMBLES at Zenith quite a bit, because Zenith LOVES him so (and sometimes simply will NOT leave him alone) -- at first I worried about him HURTING Zenith -- but so far (a little over a year) he has NOT hurt him, even though sometimes he SOUNDS as if he wants to KILL him. LOL
I have found that giving EACH cat a little "special" time with me, each day, doing what THEY like best, from me... whether it be brushing, playing with the laser light, holding in my lap, or whatever -- all 9 live in relative consistant harmony. There is sometimes the "random spat" when play gets a little too "frantic" -- but I've never had to make a trip to the vet with a kitty one of the others has injured.
There is the occasional "grumbling" over a food bowl, because as Lubo does, Zenith will gobble ALL of his down, and then "butt in" to the other's bowls, but I often open a second can, for him, and he will come running to see if I've put something "new and different" down for him, and leave the others to eat in peace. They DO all have their OWN bowls, and have learned where THEIR place is, at feeding time. (4 eat ON the counter) while I'm filling the other 5 bowls, and the others each have "their" place on the floor. It's sometimes a hassle, but it really does cut down on the squabbling at feeding time.
Good Luck with you new kitten... keep us updated with more photos and stories
LaVon