Don't assume that a senior cat will automatically reject a kitten. My sister Margaret's tuxedo Misty was 15 when she acquired her orange nephew, Seamus. After Seamus got some instruction from Auntie Misty on proper discipline (ladies eat first, ladies get to pick the window they want to look out of, no pouncing on Auntie's tail no matter how tempting...), they get along fine.

Liz