Gender sequential

[Becky]

[Gender sequential]. A being whose gender changes in a sequential order according to the gender of the person they are currently shagging. If they [shack up] with a female, the being becomes male; if they shack up with a male, they become female.
If a new gender arises, it is placed at the bottom of the sequential order of genders, and the sequential gender being would [follow suit]. Example: if partner = male, being = female; if partner = female, being = x; if partner = x, being = male.