Looking for tips on bringing in a new kitty....

[mommaU4]

to a 2 cat household.
I have two cats. Both are neutered males. We brought them home from the shelter in July of last year (2005). They were supposed to be 2 months old at the time so I guess they'd be about 8 months now.

I'd like to get one more kitten but I'm not sure how the other two will recieve a new one. Are there any of you who have done this and what sort of results did you have?

Also are there any worms that can be passed onto humans from cats? Just curious.