Something unique--my mom dodges questions about my gender by just calling me her "oldest", because I'm her oldest child. She also calls my sister her "youngest". But I think that only really works for moms somehow (can't really imagine my dad using those terms) and only for oldest and youngest children, not kids in the middle.
My dad tries to avoid identifying me to strangers, but if he does he says child or son. If I'm there that can be dodged by me responding that he's my dad, and communicating the relationship that way.
My brother calls me by my name, or "brosis", which I'm not particularly fond of, but eh.
My sister says sibling, brother, "my brother but not really", and sometimes guardian because I help raise her.
(After four years of transitioning my mom and sister use my they/them pronouns, finally, but my dad and brother still use he/him.)