The unlimited variety and complexity of social relationship, generality and being abstract law, the necessity of disputing claims and so on are considered as a necessity to interpret the law. One of the important resources that should be considered in interpreting the rules is the custom. Family Law, more than any other areas are affected by custom and social relation. This clearly proves by referring the civil law. But it should be noted that customary law is not always valid and it needs some legal provisions to have potential to referring. In this paper, the role of custom in interpreting some rights and non-financial relationship between couples, such as good companionship with one's wife, recognizing family interests, conditional contract are examined.