Nebaioth is the son of Ishmael (son of Abraham).
Genesis 25:13These are the names of the sons of Ishmael), listed in the order of their birth: Ishmael)’s firstborn was Nebaioth, then Kedar, Adbeel, Mibsam),Genesis 25:14Mishma), Dumah), Massa),Genesis 25:15Hadad), Tema), Jetur, Naphish and Kedemah.Genesis 25:16These were the sons of Ishmael), and these are the names of the twelve tribal rulers according to their settlements and camps.
Esau took his sisters as wives.
Genesis 28:9So Esau went to Ishmael) and married Mahalath) daughter of Ishmael) son of Abraham and sister of Nebaioth, in addition to the wives he already had.
Genesis 36:3and Mahalath) daughter of Ishmael and sister of Nebaioth.