Dook Goo Kau Bai never appeared in the flesh in Jin Yong's novels, and the default assumption of both fans and the characters who encountered the legacy is that DGKB was a man. I don't believe Jin Yong included any evidence to the contrary, but by the same token, I don't think Jin Yong presented any proof that DGKB *had* to be a man. Is it possible that the "Sword Demon" was a woman?