Charles Ellicott Commentary Genesis 36:18

"And these are the sons of Oholibamah, Esau`s wife: chief Jeush, chief Jalam, chief Korah: these are the chiefs that came of Oholibamah the daughter of Anah, Esau`s wife." — Genesis 36:18 (ASV)

Duke Jeush ... — Aholibamah’s three sons are dukes, but only the grandsons of the other wives. The reason for this probably is that she belonged to the dominant family of Seir, and her sons took the command of districts and tribes of the Horite people in her right.