Board Thread:Questions and Answers/@comment-25951143-20150101110046/@comment-28655833-20160605031148

Alluka is officially confirmed as a boy. Alluka probably decided to change genders since his family calls him "it" and doesn't really care about him, and Illumi calls him brother but Killua calls him sister since he's closest to Alluka and that's what he wants to be called. I'm pretty sure Alluka addresses himself as a girl too, but he was born as a male. If he was born posessing both women and men organisms then he would be labeled as a Unisex character.