Tonight with your 9 to 12 year old
The prompt
“What's one thing about your sibling that secretly annoys you, that you don't usually say out loud?”
What to listen for
If they answer easily, even with a laugh, that's them trusting this is a safe complaint zone, not a tattling session that'll blow up into a bigger fight.
If what they share sounds bigger than 'annoying', like feeling overlooked or compared to the sibling, that's worth following up on gently, since annoyance is sometimes covering something closer to hurt.
If they insist nothing bothers them, it may mean loyalty feels safer to perform than honesty right now, you can note that even close siblings get on each other's nerves sometimes, to make it feel more allowed.
What this tells you
This shows you the small friction points in a relationship your child can't just walk away from, and how safe they feel naming them.