When family social capital is too much of a good thing

•Brings construct clarity to family social capital (FSC). The form and combination of FSC matters more than just its amount.•Provides a vital reexamination of the theoretical assumptions of FSC and an empirical test of its multidimensional form.•Structural dimension of FSC exhibits a ‘too much of a good thing’ effect on family firm financial performance.•Organizational social capital (OSC) moderates the effect of the structural dimension of family social capital.•Contributes a co-dependent view of FSC and OSC to family business theorizing.