Building upon the upper echelon perspective, we examine the effect of generational involvement in management on various measures of business growth and consider different levels of family participation. Specifically, we argue that generational involvement and the participation of family actors in ownership and management foster cognitive diversity at the TMT level, which may ultimately positively or negatively impact family business growth. Our theory, which is tested using a longitudinal sample of unlisted Belgian family firms, contributes primarily to the literature related to the determinants of family firm growth, which, to date, has paid limited attention to the combined effect of different family involvement factors.