Most people don’t think twice about marking a sheet asking for their sex; male or female. But what would you think if the third option was “other”?
How do you think middle sex people feel when there is no “other” to mark? Not all people define their gender as male or female.
As muse for this site I think it would be interesting to put yourself in the shoes of the Middle Sex. Watch this HBO series of videos and you will most certainly have interesting information for your next erotic story.