adding a kitten will change the 'family dynamic'  but it absolutely could be
for the better.  My local ASPCA neuters at 2.5 lbs or about 10 to 12 weeks,
so they are pretty gender inspecific after that due to removing hormonal
influences.  As a foster mom for the local shelter, my kitty family went
from two to six.  Each time the kittens spent time in the house separate
from the resident cats, so they got used to the newest addition with out
having to worry about territorial issues.  Kittens are less likely to
threaten the hierarchy, and are more easily accepted.  By the time the
kitten is old enough to think maybe he should be 'in charge' he's been in
the house for long enough that it isn't a major deal.

Cats do have an alpha, but it is not set.  Two of mine share the 'duties' of
being top kitty.and there are occasional squabbles when one would prefer the
position.

I think a kitten would settle in very nicely into your home provided you set
him up with his own room for  a few days to see how the residents will
accept him.  They are still young, so it should go fairly smoothly.  Gauge
by their reactions how fast to proceed.  If they are grumpy, it will take
longer.  If they are interested, you can intro them faster.  Make having the
kitten a good thing by giving the residents lots of treats and praise when
ever they are not showing aggression or general grumpiness that he is
around.  I am also a huge fan of talking to cats, and explaining that to him
that the newbie was homeless, and needed help, and that you would appreciate
it if they took the time to help him, and get him acclimated into the house
and teach him some manners (cause if he is too young, you will have issues)

There are several good websites on cat introductions (google "cat
introductions"), and one book I can recommend is Cat vs Cat by Pam
Johnson-Bennett if you have any questions on how they interact.
http://www.amazon.com/Cat-Vs-Keeping-Peace-When/dp/0142004758

It's been my experience that a kitten is *far* easier to integrate than
an adult cat. The kitten is really no threat to the existing cats, and
kittens just have a way of rolling around and saying "Look how cute I
am; please don't kill me." The sex of the kitten you choose really
isn't a factor, as long as it's neutered before becoming sexually
mature. Good luck! I think you'll find that three is really no more
trouble than two.

Sherry

For info visit this page: http://www.flippyscatpage.com/health.html and look
under INTRODUCING PETS.

Flippy in Melbourne, Australia.
Catpage: http://www.flippyscatpage.com