Apologize to your little sibling when you’re wrong. They’re learning from you what grown-ups do.

Younger kids learn what adulthood is by watching the nearest version of it. To a nine-year-old, you are not a peer; you are a demonstration, and every time you are wrong and say so out loud you are teaching that being wrong is survivable. If they only ever see you defend yourself, that is the lesson instead.

Go and do it the next time you snap at them, in plain words, on the same day. Say what you did and that it was not their fault. You do not need to explain yourself, and they will remember the shape of it for a long time.