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.
He is physically a male, and mentally female. It is the reason why Killua referred to him as "she". This is stated in the databooks and also by the canon writers. So in other words, Alluka is transgendered. Though, I believe people have the right to think of him as whatever they like, male or female.