Board Thread:Questions and Answers/@comment-25951143-20150101110046/@comment-26540142-20150628082740

Alright, Alluka is born a male but identifies as female. The reason her parent's do not consider her female is because they do not consider her part of the family. However within the 13th chairman arc Killua states "Because she's a girl and I don't trust her with you." meaning Killua deffiantly considers her female and in response to Killua's retort Tsubone says "Then I guess that's why I'm coming along." meaning Kikyo sent her to protect Killua and Alluka. Possibly meaning that she considers Alluka female privately.