Esau went to Ishmael and married Mahalath, the sister of Nebaioth and daughter of Abraham’s son Ishmael, in addition to the wives he already had.
This passage concerning Esau comes in in the midst of Jacob's story, either, 1. To show the influence of a good example. Esau, though the greater man, now begins to think Jacob the better man, and disdains not to take him for his pattern in this particular instance of marrying with a daughter of Abraham.
Commenting on Genesis 28:6-9
Then went Esau unto Ishmael,.... Not to Ishmael in person, for he was now dead, Gen 25:17, and had been dead as is reckoned about fourteen years before this, but to the house of Ishmael: and took unto the wives which he had; the daughters of Heth, and who seem by this to be both alive at this time: Mahalath the daughter of Ishmael, Abraham's...
Then went Esau unto Ishmael, and took unto the wives which he had Mahalath the daughter of Ishmael Abraham's son, the sister of Nebajoth, to be his wife. (c) Thinking by this to have reconciled himself to his father, but all in vain: for he does not take away the cause of the evil.