'Firstborn Son' in the Bible

These were chiefs of the sons of Esau: the sons of Eliphaz the firstborn son of Esau; chief Teman, chief Omar, chief Zepho, chief Kenaz,

If a man has two wives, one beloved, and another hated, and they have borne him children, both the beloved and the hated; and if the firstborn son be hers that was hated:

And his firstborn son Abdon, and Zur, and Kish, and Baal, and Nadab,

And his firstborn son Abdon, then Zur, and Kish, and Baal, and Ner, and Nadab,