The eldest child’s experiment may become the youngest child’s rule.

The eldest tests the boundaries and the parents recalibrate, so the youngest inherits rules that were written in response to somebody else’s adolescence. Restrictions that feel arbitrary to them were shaped by an episode they were too young to remember or were never told about.

If you are a parent, explain where a rule came from rather than defending it as policy. And if you are the younger sibling, asking what happened before you were paying attention often converts an inexplicable family rule into something that at least makes sense, even if you still disagree with it.