John Gill Commentary Genesis 36:15

"These are the chiefs of the sons of Esau: the sons of Eliphaz the first-born of Esau: chief Teman, chief Omar, chief Zepho, chief Kenaz," — Genesis 36:15 (ASV)

These were dukes of the sons of Esau
Ben Melech says, the difference between a duke and a king was, that a king is crowned and a duke is not crowned; but Jarchi interprets the word of heads of families, which seems probable; so that as Esau's sons and grandsons are before related, here it is suggested that they had large and numerous families, of which they were the heads and governors; and in this and the following verses, (Genesis 36:16–19) ; the sons and grandsons of Esau by his several wives are rehearsed as in the preceding verses, with the title of "duke" given to each of them.