Some creatires here on Earth can literally switch genders due to the reproductive/survival needs of their species, The Hive can also switch genders, though it isn't super clear to me why or how. Most knight-types seem to be male, and most wizard/witch-types seem to be female, but that's not an absolute, and the lore is pretty vague. Aurash is female, who becomes Auryx, who becomes Oryx, who is male. Novota, Xivu Arath, Hashladun, and Savathun are all Female, while Nokris is Male. Where they started and where they'll end isn't clear, probably because hive lore is mostly "Let's talk about death/murder/genocide and how much we love it.", and kinda glazes over all the other important details. Thus, the understandable confusion.