Step 1: Frame kinship as society's foundational network:
Before formal institutions like the state existed, kinship ties were often the primary basis on which entire societies organised cooperation, authority and resource-sharing.
Step 2: Connect structure to function:
The structural rules of kinship (who counts as consanguineal/affinal kin, patrilineal/matrilineal descent) directly produce its practical usages - deciding whom one may marry, who inherits property, and who is obligated to support whom in times of need.
Final Answer:
Kinship is the blood-and-marriage-based network that structures a society's marriage rules, inheritance patterns, social roles and mutual obligations, functioning as a core pillar of social organisation.