It's just an attempt by the PC crowd to complicate something that's pretty simple.
There are two genders (even trans-sexuals want to be one or the other, even if it's not the one they began with) and virtually all the action is between them -- one way or the other.
There are three basic ways of copulat ing: He/she; he/he (sounds like laughter, doesn't it?); and she/she; or ShEeE, which is really confusing. That is, straight, homosexual, or bi-sexual.
Unless you want to throw in aberrations like bestiality, necrophilia, incest, and paedophilia -- and a marshmallow dreamer would be too nice to do that -- the options are pretty-well covered in my third paragraph.
