The first child born to a set of parents, or the oldest child in a family.
From Old English 'fyrst' (first) and 'boren' (born). The compound emerged in medieval English to describe inheritance and succession rights, as firstborn sons traditionally inherited family property and titles.
In ancient societies, firstborn children—especially sons—had massive legal and economic advantages because of primogeniture, a law that gave all family wealth to the oldest son. This shaped entire civilizations: younger sons had to become warriors, priests, or adventurers, which literally changed history.
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