The management of family business groups is extremely complex. Internal complexity, which is a cause for failure of organizations, has been under explored. We study how family business groups manage their internal complexity to be able to survive over time. In this study, we bring together the case study method and complexity science to suggest new ways to study family business groups. We focus on a Finnish family business group and provide an empirical illustration, based on a large family business case, of how structural and cognitive complexity is dealt with.