1. Reuben was Israel’s first son. Reuben should have received the special privileges of the oldest son. But he had physical relations with his father’s slave woman. So those special privileges were given to Joseph’s sons. (Joseph was a son of Israel.) In the family history Reuben’s name is not listed as the first son.
2. Judah became stronger than his brothers. And a leader came from his family. But Joseph’s family received the privileges that belonged to the oldest son.
3. Reuben was the first son born to Israel. Reuben’s sons were Hanoch, Pallu, Hezron and Carmi.