'Firstborn of Israel' in the Bible

The descendants of Reuben, the firstborn of Israel: according to their family records by their clans and their ancestral houses, counting one by one the names of every male 20 years old or more, everyone who could serve in the army,

Reuben was the firstborn of Israel.Reuben’s descendants:the Hanochite clan from Hanoch;the Palluite clan from Pallu;