Who was the firstborn son of Jacob?

Reuben was the firstborn son of Jacob. In Genesis, he is the eldest of Jacob’s sons and the first son born to Leah, Jacob’s wife; his birth is presented as an answer to Leah’s distress and her hope of winning Jacob’s affection.

Reuben’s position as firstborn gave him special status, but the biblical narrative later says he forfeited the right to excel because he slept with Bilhah, his father’s concubine. First Chronicles 5:1–2 explains that the birthright was transferred to Joseph’s sons, while leadership came through Judah and priestly service through Levi.

Reuben was not the most prominent of Jacob’s sons in the later national story, although he sometimes acted as the eldest brother. He tried to prevent the others from killing Joseph and proposed placing him in a pit. The tribe of Reuben eventually received territory east of the Jordan River. Judah, Simeon, and Levi were younger brothers, not Jacob’s firstborn.