5:1 he was the firstborn. The writer explains why Reuben the firstborn is given so little prominence among the tribes. He defiled his father’s bed (Gen. 35:22; 49:4) and lost his right as firstborn to the double portion of the inheritance (Deut. 21:15–17). Instead, Joseph received Reuben’s double portion through his sons Ephraim and Manasseh, who were treated as separate tribes (Gen. 48:1–22).