Joktan ben's father was עבר. His paternal grandparents were שלח and Muak ben Kesed. He is an only child.
General Notes
Book I, Chapter 6 4. ...Now Joctan, one of the sons of Heber, had these sons,Elmodad, Sal eph, Asermoth, Jera, Adoram, Aizel, Decla, Ebal, Abimael, Sabeus, Ophir, Euilat, and Jobab. These inhabited from Cophen, an Indian river, and in part of Asia adjoi
Joktan ben Eber