The youngest family member meets people already carrying decades of shared references.

Arriving last into a family means arriving into a conversation that started long before you. The jokes have histories, the tensions have precedents, and everyone else knows why a certain name makes the room go quiet. That is not exclusion, but it does mean the youngest person is translating while everyone else is only remembering. Belonging comes later and in pieces, usually through being told the stories rather than deducing them.

If you are the newest, ask rather than pretend to follow. If you are not, notice when a reference lands on someone with no way of catching it, and take a minute to explain it kindly.