How to change your gender on facebook?

[☮Leigh]

I noticed that some people are able to make their facebook use gender neutral pronouns instead of him/her. For example if you arent friends with someone it usually says this:

To see what SHE shares with friends, send HER a friend request.

But I have seen a couple people with this:

To see what THEY share with friends, send THEM a friend request.

How do I make my facebook use they and them instead of her or him? When I go into my settings it only lets me choose male or female...I am genderqueer so that is why I am asking.