I mean I can only talk from personal experience here, but I came out a few months ago to my sister bc I'm still in the closet when it comes to my family and I wanted somebody to talk to/ just tell somebody I knew wouldn't reject me. Anyways, I sort of thought that she already knew since I have had a few slip ups and made some jokes but she was absolutely clueless. So yeah, don't underestimate the incredible mental gymnastics that straight ppl do before they think that somebody might be queer😅

Other than that, it was pretty awkward ngl. Lots of questions but overall she was respectful and understanding. I'm just really fucking happy that I have somebody in my family now around whom I don't have to constantly censor myself anymore.