One, regarding Alluka Zoldyck...
Imo, I think the story makes it as clear as you can without literally saying the word trans and while keeping it kind of respectful.
The majority of the family calls her a boy. We hear that the Zoldyck family has all sons. The HxH databook has her sex listed as 'male'. In most cases she is referred to neutrally, but Illumi and Milluki specifically refer to her as their little brother (in original Japanese too).
However, Killua, the family member who 'loves her most' and the only one who isn't trying to have her killed/okay with her use as an object, calls her a girl and emphasizes that she is a girl. Alluka also uses traditionally female pronouns, and dresses in feminine clothing when she is older, whereas she wears more vaguely masculine clothing when she is younger (the house staff calls her by male terms when she is younger too).
The manga repeatedly makes the point that Killua knows more about Alluka than anyone else, regarding powers, or personhood, or anything. So that seems to naturally extend here to his treatment of her.
Girl is put in [ brackets ] in the original, emphasis.
"there’s a chapter in volume 31, chapter 322 specifically, titled…well, the furigana is きょうだい (kyoudai). “Siblings,” which is also the chapter’s title in the official english release. normally, that’s written in kanji as 兄弟, which in terms of literal meaning is composed of the kanji for older brother and younger brother.
that’s not the kanji used in the chapter title, though
for the chapter title, togashi used the kanji 兄妹, which can also be read as kyoudai although that’s not the normal reading. but instead of the kanji for younger brother he used the kanji for little sister instead"
https://itsybitsyjoltik.tumblr.com/...an-interesting-thing-i-noticed-in-my-japanese
^ The reason this is particularly relevant is this is an example of Togashi also acknowledging Alluka is female, since its a title of a chapter.
Two, I'm a bit surprised by the fact Kalluto has a ? tag regarding gender. Sure, things can change there, maybe Kalluto is more complicated, I'm not entirely opposed to the ?. But as is, he's a boy who emulates his mother's style of dress. (Kalluto uses boku, and is as referred to as a little brother on a few occasions)
