The non-financial foundation of family business performance is largely under-researched. More clarity is needed to identify the theoretic origin and outcomes of the familiness concept. This conceptual analysis explores the non-financial competitive advantage of familiness functioning optimally as familiness capital (FamCap). The notion of familiness is explored in terms of psychological capital (PsyCap) with FamCap as outcome variable. Family businesses seem to nurture familiness resources in the form of the PsyCap constructs of self-efficacy, hope, optimism and resilience. These resources could advance the optimal functioning of FamCap. The presence of FamCap should sustain a positive competitive advantage in a family firm.