User blog comment:Bennlimos/Understanding the Zoldyck Family's Nen Situation/@comment-10528819-20151018141034/@comment-4828844-20151018144259

About the third point, I remember someone mentioning this in a previous blog: that perhaps Killua knew about Zeno's Dragon Dive because they had the chance to talk like "normal" family, like the time he explained to Gon how the undergound of NGL (or was it East Gorteau?) works and that Zeno had once infiltrated the place for a job. Killua mentioned that a brother heard it from their grandfather; I am betting Milluki, because, apart from Alluka, Killua seems to be quite in okay terms with him.