I would encourage you to adopt two kittens. It would be easier on your household. I say that sincerely. Kittens are VERY bratty. I think your adult cat would tire of a kitten very quickly- if it is like any of my 6 adult cats.

I adopted Tuck, a 2 month old tabby. Within a week, I went to the shelter to adopt another kitten- Ari. They are best friends, and the adult cats thanked me tremendously.

I would encourage you to solicit advice from people that have adopted a single kitten with an adult cat....I imagine you will find that they say 2 kittens would have been a better idea.

My kittens (well, they are 11 months old now) still prefer each other...but they do play with the other cats, too.

Just my .02, and not some ploy to get you to adopt more cats than you want.