How many Black Knights (Black Wings Generals) are there really?

Anything that happens outside the game or during events means nothing, in no way during actual in game events has Aran been shown as female so canonically Aran is a male.

Actually, in the meeting hall (The place where all the classes and instructors get together) Aran appears as female. However, in the past leafre area there is a quest where you have to do something for Maha and during that quest Aran is male.
God damnit Nexon!