Genesis 28:9

Then went Esau unto Ishmael
Not to Ishmael in person, for he was now dead, ( Genesis 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 son;
the same with Bashemath, ( Genesis 36:3 ) ; as the Targum of Jonathan expresses it, this person having two names, and is further described, the sister of Nebajoth, to be his wife;
who was the eldest son of Ishmael, and, his father being dead, was the principal in the family; and this woman Esau took to wife was his sister by his mother's side, as the above Targum expresses, as well as by his father's; whereas he might have other sisters only by his father's side, he having had more wives than one. This Esau seems to have done in order to curry favour with his father, who was displeased with his other wives, and therefore takes one of his father's brother's daughters; but in this he acted an unwise part, on more accounts than one; partly as it was taking to wife the daughter of one that was cast out of his grandfather's house, and had been a persecutor of his father, and therefore not likely to be agreeable to him; and partly as being a daughter of the bondmaid's son: children born of her could not inherit the land promised to Abraham and Isaac.