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.
Jewish Publication Society of America Version (JPS1917) - Genesis 28:9 >so Esau went unto Ishmael, and took unto the wives that he had Mahalath the daughter of Ishmael Abraham's son, the sister of Nebaioth, to be his wife.