Question: In the anime *Hunter x Hunter*, Alluka Zoldyck is considered as a girl by Killua, shown when they leave their estate and were accompanied by four butlers. Killua shouted to Gotoh and said that he needs a female butler to join them because Alluka is a girl.

However, I am confused because Milluki address Alluka as a brother, in the episode when he wished to Nanika to kill the tourist photographer. He clearly told the the tourist that he was just taking his brothers for a walk. In addition, the [Hunter Wiki](http://hunterxhunter.wikia.com/wiki/Alluka_Zoldyck) acknowledged Alluka as a male.

What is Alluka's actual gender?

Answer: 
I've always played with two theories:

1. It could be the case that the family refer to Alluka as male to distance themselves from her, denying the fact that she's female to dehumanize her, or to further disassociate her from the family in some way.
2. Or it could very well be that, as Alluka's exact origin is unknown, she isn't strictly human and doesn't possess what we would call a conventional gender, but rather, her gender is simply non-existent, like a Nen beast.

Personally, I favor the latter, or a mix of the two. These are all just speculation, of course, but it's interesting to think about nonetheless.
Here is my assumption: When Alluka was born, her mother didn't take care of her, she let the butlers to take care of her (like bathing her, etc), and because their mother always thought that all her children must be male, so she thinks that Alluka is male too, especially because she is cold to her and never bathe her, so she doesn't know that Alluka is actually female, and the butlers are too afraid to tell their mother that Alluka is female. While Killua is the one who really cares for her, and knows her the most.

So even thought in the birth-biodata and everywhere, Alluka is stated as a male, but Killua knows the truth, and so the butlers who ever took Alluka to bath also have known that.

It's just my hypothesis after watching the anime. I think if this hypothesis is true, this story will be a very nice scene, because then it will be stated that "Even the writer of the story doesn't know about Alluka's gender, but her brother knows it because of how he always set an eye on her."