Have your son play with more than one cat/kitten. Help hime to choose different types, and after that he will have a feeling of the bond he wants with his cat. The two will mesh their personalities. An aloof cat may just want to sit and be petted, the overachiever may want to play and run. There will likely be one cat that stands out as the best match. Have whichever sex neutered and there is not much difference overall. Just different personalities for each animal.