gender

This term is proposed for full integration into Schema.org, pending implementation feedback and adoption from applications and websites.

Thing > Property > gender

Gender of something, typically a Person, but possibly also fictional characters, animals, etc. While http://schema.org/Male and http://schema.org/Female may be used, text strings are also acceptable for people who do not identify as a binary gender. The gender property can also be used in an extended sense to cover e.g. the gender of sports teams. As with the gender of individuals, we do not try to enumerate all possibilities. A mixed-gender SportsTeam can be indicated with a text value of "Mixed".
Values expected to be one of these types
GenderType
Text
Used on these types
Person
SportsTeam

Source

https://github.com/schemaorg/schemaorg/issues/2341