New Defender's Study Bible Notes
11:29 took them wives. Nahor married his niece, and Sarai was Abram’s half-sister (Genesis 20:12), a daughter of Terah by another of his wives. Close marriages were not yet genetically dangerous and so were not prohibited until the Mosaic law was established. Perhaps they were even desirable in those families who still worshipped the true God, in order to maintain a pure faith.