These were the sons of Reuben the firstborn of Israel. He was the firstborn, but his birthright was given to the sons of Joseph son of Israel, because Reuben defiled his father’s bed. He is not listed in the genealogy according to birthright.
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,
He must acknowledge the firstborn, the son of the unloved wife, by giving him two shares of his estate, for he is the firstfruits of his virility; he has the rights of the firstborn.