2 kittens are ALWAYS better than one (for many reasons) so THANK YOU for wanting 2!!

It is preferable to have 2, if not 3, litter boxes for a home with 2 cats. And food and water dishes as well. While it is all together possible for some to get away with one, why make them compete? Having extra helps prevent rivalry.

A male/female pair is perfectly fine. But be aware that a female can get pregnant rather young, so do not postpone neutering once they are of age.

Congratulations on your additions, and have fun!!