>>3867572(nonstandard) they (singular). Gender-neutral third-person singular subject pronoun, coordinate with gendered pronouns he and she.
1992, Sinclair, Jim, “If you could choose...”, in Jim Sinclair's Web Site[1], archived from the original on 2003-11-03:
Anyone I would be interested in would have to be a pretty special person. I wouldn't want to miss out on knowing such a person just because xe happened to be the "wrong" sex.