Genesis 36:15

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.