Charles Ellicott Commentary Exodus 6:14-15

"These are the heads of their fathers` houses. The sons of Reuben the first-born of Israel: Hanoch, and Pallu, Hezron, and Carmi; these are the families of Reuben. And the sons of Simeon: Jemuel, and Jamin, and Ohad, and Jachin, and Zohar, and Shaul the son of a Canaanitish woman; these are the families of Simeon." — Exodus 6:14-15 (ASV)

Reuben ... Simeon. —It fixes the position of the family of Levi in the house of Jacob to commence the genealogy with a mention of the two elder brothers. As, however, the writer is really concerned only with the Levites, the families of Reuben and Simeon are dismissed with the briefest possible notice. Nothing new is recorded of them. (See Genesis 46:9-10.)