Every One Piece arc usually brings something new to the table—a different setting, new subplots—and most importantly, a lot of new characters. In the current Wano arc, not only are we introduced to the various people of Wano but also key characters that are essential to the development of the story as a whole.
One of the key characters in the Wano arc would have to be Yamato, Kaido's heir.
Due to Yamato's physical appearance, fans may be confused with what his gender identity is. So I'm here to clarify that for you!
Warning: there will be minor manga spoilers about Yamato's character.
Putting it simply, Yamato is transgender. He greatly idolizes Kozuki Oden, who is a man. Yamato wishes to embody Oden's goals and actions, and even his clothing, among other things. Plus, he aims to continue Oden's wishes; which was to open Wano's borders to the world. So Yamato figured that if he wanted to idolize Oden to the highest level and carry on his will, then he must become him—and that includes becoming a man as well.
Yamato refers to himself with he/him pronouns, and so do the Beast Pirates. Despite Kaido's blatant disapproval towards Yamato idolizing Oden, Kaido nevertheless refers to Yamato as his son—not his daughter.
One Piece is one of the prominent anime series that have LGBT representation, and Oda's definitely improved with it through the years. Just a friendly reminder that just because Yamato isn't "male passing", this does not mean he's a girl.
As of Episode 979 in the anime, Yamato still hasn't made a major appearance. However, we do see a preview of him in the latest opening theme. Considering the part of the story where the anime is right now, I think we're gonna be able to see him soon!
Related: Will One Piece Ever End?