Throne People

"Throne people" are those who start life in one gender, but later switch to a different one. This can be for any reason, any number of times, and to and from any gender.
The name comes from the myth of The Birth of Queen Merewald, in which an orphan girl becomes Queen Merewald I of Enbinaar after sitting on a throne that contained the soul of a magician. The magician had been a boy in his previous life, but since Queen Merewald I preferred the company of women, the magician came back as a woman named Queen Consort Walmered . Her body, however, was not altered from the one she previously held.
Due to throne people's important role in the creation of their kingdom, they are regarded as respectable, honourable souls sent by the divine will of Queen Merewald I to bless their families. Their sacred existed resulted, on the long term, of a much more flexible gendered culture that defaults to treating one's gender identity as entirely separate from the bodies they are born with.
Even though modern societies do not assign children a gender identity based on their bodies, throne people still exist and are still highly regarded. However, instead of being "someone born with a boy's body who lives as a girl" (and vice-versa), throne people are now more commonly defined as people whose gender changes throughout their lifetime. It is relatively common for people to experiment with their gender identity and expression, and those most curious who accumulate experiences living in multiple genders are thus given the honour of being recognised as throne people.
The term for a person whose gender identity never changes (or, in the old days, for people who lived in the same gender as assumed to fit their bodies) is "sealed person". It refers to the "unaltered" gender of Queen Consort Walmered while her soul was still sealed in the throne, though some people interpret it as having one's ability to explore gender being "sealed away", making them unable to switch and enriching their life experiences.