Male or female cat?

Question
I have two felines in my home currently and want to add another. One cat is a male, 15 years old, extremely social but mellow with some medical issues i.e. diabetes and hyperthyroidism under medication.  I adopted he and his sister when they were 8 weeks old.  His sister unexpectedly died 1 yr ago.  Our second cat is a feral female who came to us at 3 mos old, she is now just 2.  At that time she was slowly integrated with the older two and for 6 mos (when my older girl died) they all lived peacefully together.  She is very loving towards my husband and I but extremely skiddish with strangers, strange noises and anything out of the ordinary.   We would like to get another cat to be more of a companion/playmate for our little one because the reality is our older cat will someday pass and that is not the time to be getting another cat.  Our biggest anxiety over getting another cat is, which gender is better for our situation?  We don't want any Alpha problems because that may cause or oldest added stress which he does not need and likewise, we don't want any Queen problems with our little girl because we would hate for her to withdraw.  As it is, our senior does play with her from time to time but you can tell he's "over it".  We do not want to get a kitten, so is a young (1-2) year old cat appropriate?  Please let me know your thoughts.  FYI, both cats are fixed with claws.  Thanks!

Answer
JPK,

My contention has always been that once a cat is neutered/spayed, gender really does not matter.  I would get a kitten between 4 and 6 months of age and, if introduced properly, it should get along fine with the other cats.  If the kitten weighs at least 4 pounds, it can be neutered/spayed at that age. Established cats tend to be much more tolerant of kittens than they are of older cats.

If you need a good protocol for introducing another cat into a home with established cats, please let me know.

Best regards... Norm.