Being a family business is not good or bad per se; it is an extra characteristic that management has to deal with. In fact, family influence can become a blessing or a curse for a company, depending on how family members handle Key Success Family Factors (KSFF). This paper presents the Two Stages Scoring (TSS) model, a tool that companies can use to develop a competitive advantage based precisely on family influence. TSS Model is based on results obtained in a Mexican Family Businesses research, in which the relationship between family influence and firm performance was tested. The variable “family influence” was measured through the common F-PEC instrument and by FAMILIAL INDEX, while the “firm performance” was measured by CEO level of satisfaction on six financial performance dimensions. Conclusions of the research include that family influence- firm performance relationship is not high for this sample of companies and, as a consequence, the TSS model is proposed based on the idea that firm performance is related more effectively to the KSFF.