'Firstborn of Israel' in the Bible

Reuben, the firstborn of Israel (Jacob), the sons of Reuben: of Hanoch, the family of the Hanochites; of Pallu, the family of the Palluites;

Now [we come to] the sons of Reuben the firstborn of Israel—for Reuben was the eldest, but because he defiled his father’s bed [with Bilhah his father’s concubine], his birthright was given to [Manasseh and Ephraim] the sons of Joseph [the favorite] son of Israel, so that he is not enrolled in the genealogy according to the birthright.

the sons of Reuben the firstborn of Israel: Hanoch, Pallu, Hezron, and Carmi.