We distinguish between family companies involving multiple family members as owners and/or managers and lone-founder companies involving only the founder and no other family members. We apply social identity theory and organizational identification to elucidate the differences between these two firms and how the differing organizational identities reflect unique desires for control and influence in both types of firms. We then consider how these differences are reflected in the firm's board structure (i.e., directorship interlocks, director experiences, and director tenures). Specifically, we predict that family firms are more likely to interlock with other family firms, select directors with more experience in family firms, and keep directors on their boards longer. Conversely, we predict that family firms are less likely to interlock with lone-founder firms or select directors with experience in lone-founder-controlled firms. Lone-Founder firms follow a similar pattern. We also consider the consequences of family and lone-founder ownership and board structures on the investment behavior of three classes of institutional investors. We test our hypotheses with a sample of publicly-traded corporations between 1991 and 2006, and report strong support for most of our predictions.