Leah became pregnant and gave birth to a son. She named him Reuben [Here’s My Son], because she said, “Certainly, the Lord has seen my misery; now my husband will love me!”
These are the sons of Reuben, Israel’s firstborn. (Although he was the firstborn, his rights as firstborn were given to his nephews, Joseph’s sons, because he dishonored his father’s bed. However, Joseph couldn’t be listed in the genealogy as the firstborn son.
The roster of families and households for the descendants of Reuben, Israel’s firstborn son, listed every man by name who was at least 20 years old and eligible for military duty.
Instead, he must recognize the son of the wife he doesn’t love as the firstborn. He must give that son a double portion of whatever he owns. That son is the very first son he had. The rights of the firstborn son are his.