The lineage's context family: other lineages that have carried the same content, each with a copy state (in-sync / stale / modified) relative to the family's reference member, evidence dates, and coordinates for linking. Family membership and canonical flags may briefly lag recent changes; copy states and evidence reflect current content. Members, counts, and the reference member include only what the caller can access. A lineage not yet in any family returns 200 with empty data and zero counts. 404 when the lineage does not exist or is not visible to the caller.