Nowadays it's not uncommon to meet people who don't identify with either pole of the standard "he" and "she" binary. "It," our only singular neuter pronoun, doesn't work for sentient creatures. "They" is often used as a gender-neutral pronoun in these cases. My elementary school and high school teachers hammered into our heads (and your teachers probably did the same to you if you're close to my age) that singular "they" is ungrammatical and should never be spoken or written by literate persons. Those who hold the contrary position point out that singular "they" for subjects of unknown gender has been around for at least 600 years. I can grit my teeth, defy my early training, and accept that usage in a case like this:
"Somebody left their car keys in the lounge."
That sentence refers to a hypothetical or unidentified person. This example, however, seems fundamentally different to me:
"Lee left their car keys in the lounge."
A pronoun that's nominally plural applied to a single, known individual just sounds weird. The one exception that comes to mind, the "fusion" characters in the animated series STEVEN UNIVERSE (made up of two or three individuals temporarily fused into a composite person), isn't likely to be met in everyday life.
If we don't want to say "they" in place of "he" or "she," though, what do we do? (Well, aside from asking what pronoun a given person prefers, as the page linked below suggests.) The phrase "he or she" might work in writing but would be cumbersome in speech. Besides, as mentioned, some people don't identify with either one of those. We could repeat the proper name every time instead, as some church liturgies do to avoid assigning a sex to the Supreme Being (including the odd compound "Godself"). Madeleine L'Engle often refers to God by the ancient Hebrew word "El" instead of "He" or "She." In ordinary conversation, though, constantly repeating a person's name sounds awkward. What about inventing a neuter or inclusive pronoun, which has often been tried?
This page discusses gender-inclusive and gender-neutral pronouns, with a brief historical overview of these words and a chart of gender-neutral pronouns that have been coined and used in some speech communities:Gender Pronouns
There's a surprising variety of neologisms proposed to solve this problem, and no consensus term has been adopted in popular speech. As linguistic scholars tell us, the basic building blocks of a language resist change. In the course of its development from Anglo-Saxon, English has freely adopted such parts of speech as verbs, nouns, and adjectives from Latin, Greek, French, and many other languages. A familiar joke declares, "English doesn't borrow from other languages. It mugs them in dark alleys, rummages through their pockets, and takes what it wants." Structural elements such as pronouns, however, are a different matter—with some little-known exceptions mentioned on the page cited above.
The languages of aliens with more than the two sexes displayed by typical Earth mammals would include other gender pronouns. Writers who create such aliens can invent words to match. Transforming languages actually spoken in our own cultures isn't so easy.
Margaret L. CarterCarter's Crypt