A Chief Must Have More Than One Wife

In the ancient Afro-Asiatic world rulers had more than one wife and usual at least two concubines.  What was originally a way to mark out one's territory using the settlement of wives in separate locations on a north-south axis, became a status symbol in the time of King Solomon.  The prophets criticised him for having so many wives and concubines, but it was his father David who broke his royal ancestors' marriage pattern of having only two wives.

All the kings listed in Genesis held to the pattern of only two wives. One was a half-sister (as was Sarah to Abraham) and the other wife was a patrilineal cousin or niece (as was Keturah to Abraham). This means that the rulers had two first-born sons, but only the son of the half-sister wife ascended to his father's throne.  The first-born son of the cousin/niece wife ascended to the throne of his maternal grandfather or launched out as a warrior (like Nimrod) to establish a territory for himself.  This is what makes Abraham's story so remarkable.  His older brother ascended to the throne of their father Terah. Haran, Abraham's older half-brother, would have ascended to the throne of his maternal grandfather, Haran, only he died in Ur.  Abraham was not considered to rule Haran's territory because it was contrary to the ancestors' pattern.  Instead, God promised Abraham a territory by divine provision.

To understand why we must investigate the genealogical pattern of Abraham's people, go here and here.