Tonight with your 9 to 12 year old
The prompt
“Is there a game in our family that only we understand the rules to?”
What to listen for
If they can describe it in detail, including the made-up rules that wouldn't make sense to anyone else, that shared language is a strong sign of belonging, it's proof this family has its own culture that's theirs.
If they say there isn't one, that's a nudge to invent a tradition together, not a sign anything's wrong.
If they say "I don't know," describe a game you remember playing together and ask if they remember the made-up rule that came with it.
What this tells you
This tells you how much of their sense of belonging is tied to inside knowledge only your family shares.