Leah became pregnant and gave birth to a son. She named him Reuben, for she said, “It is because the Lord has seen my misery. Surely my husband will love me now.”
The sons of Reuben the firstborn of Israel (he was the firstborn, but when he defiled his father’s marriage bed, his rights as firstborn were given to the sons of Joseph son of Israel; so he could not be listed in the genealogical record in accordance with his birthright,
From the descendants of Reuben the firstborn son of Israel: All the men twenty years old or more who were able to serve in the army were listed by name, one by one, according to the records of their clans and families.
He must acknowledge the son of his unloved wife as the firstborn by giving him a double share of all he has. That son is the first sign of his father’s strength. The right of the firstborn belongs to him.