There have been many attempts to define the concept of family. The approach taken here is that there is no possibility of defining the family. A solution is suggested, which is to say that if a group consists of at least one parent-child unit and/or at least one spousal unit the group is a family. The parent-child unit is defined as one parent and one child related to each other and the spousal unit is defined as two adults cohabiting (maritally or non-maritally). For research or policy use, and also theoretically, this approach can solve the problems in clarifying what a family is in a specific case.