Purpose: This paper sought to verify the influence of family structure on the performance of family companies listed in Brazil between 2010 and 2017. We also analyzed the impact of monitoring and duality on the performance of these companies. Originality/value: The relevance of the study is found mainly in the use of unusual variables, such as the participation of founders and descendants as shareholders, on the boards of directors, and as chief executive officers (CEOs), since it was not possible to identify any study in Brazil that addressed family participation in a fragmented way, separating the effects caused by founders and descendants, giving greater depth to the issue. In addition, it generates interest to the most varied audiences, including shareholders, regulators, analysts, and investors who have a specific interest in how family structures affect the performance of companies. Design/methodology/approach: Data related to shareholders, composition of the boards of directors, executives, family ties, founding families, founders, descendants, and financial performance were used in the research. An unbalanced data panel was analyzed through the generalized method of moments (GMM). Findings: A positive effect of monitoring and duality on the firms' performance was verified. The impact of family structure on performance was ambiguous. Founders and descendants that were CEOs or were working in management had positive and negative effects on the performance measures. Additionally, the participation of founders on the board of directors negatively impacted the performance. Finally, it was observed that family ownership positively impacts the firms' performance, suggesting that families look after the companies. [ABSTRACT FROM AUTHOR]