@CalmBit And you've got a solid argument there with "they" being a more respectful form. But there are *killer* arguments that better address the fact that "he" is *not* gender-neutral- https://motivatedgrammar.wordpress.com/2009/09/10/singular-they-and-the-many-reasons-why-its-correct/
"Is it your brother or sister who can hold his breath for four minutes?" is just really, really wrong. You can *feel* how gendered that word is there. So regardless of propriety we need language to step up to the plate.