The analysis is concerned with four institutions in the sphere of family law: Guardianship, marriage of levirate, marriage of a woman in order to provide her father or brother with an heir and marriage between close relatives (incest taboo did not exist). The issue of the research is to show how the social conditions and internal family economy with its power balance are reflected in the rules of the Sasanian law, and that the differences apparent in the later texts are not accidental, but form a pattern caused by the changing social conditions, and that the law was changed in order to help preserve the Zoroastrian minority in adversity under Arab rule.