Thanks for the added info! Yeah, it's complicated, but it's also fun in a way - I wish English had more nuances like this (I wish they still had the formal/informal 'you' distinction, for example) because it can be such a boon for writers.

I love that 'older martial sister' thing, that's very cool. And when she calls WWX "Xianxian" it's obviously affectionate and sisterly, but also age-related, right? Like, she's his elder sort-of-sister, so she can call him that, but WWX wouldn't go around calling her YanYan, even if he is an irreverent type, because he's younger and it would be disrespectful? I hope I got that right.