Gaham is the grandson of Terah and the son of Nahor. He is one of the eight sons born to Milcah, the daughter of Haran, and Nahor.
Gen 22:20Now after these things it was told to Abraham, “Behold, Milcah also has borne children to your brother Nahor:Gen 22:21Uz his firstborn, Buz his brother, Kemuel the father of Aram,Gen 22:22Chesed, Hazo, Pildash, Jidlaph, and Bethuel.”Gen 22:23(Bethuel became the father of Rebekah.) These eight Milcah bore to Nahor, Abraham’s brother.Gen 22:24And his concubine, whose name was Reumah, also bore Tebah, Gaham, Tahash, and Maacah.
[See Abraham's Genealogy]