Purpose: Present research was conducted with aim of investigating the fit pattern of family function and relationship beliefs mediated by differentiation of self with social interest. Methodology: This study was cross-sectional in terms of purpose was applied and in terms of implementation method was quantitative from type of correlation. The study population was students of Islamic Azad University of Khomeini Shahr in the academic years 2019-20. The research sample was 300 people who were selected by cluster sampling method with respect to the volume of students in different faculties. To collected data were used from the family function questionnaire (Epstein et al, 1983), relationship beliefs questionnaire (Eidelson & Epstein, 1982), differentiation of self-inventory (Skowron & Fridlander, 1998), and social interest index (Greever et al, 1973). Data were analyzed by structural equation modeling method of path analysis in SPSS and PLS software. Findings: The results showed that pattern of family function and relationship beliefs mediated by differentiation of self with social interest had a well fit. In addition, family function and relationship beliefs had a direct and significant effect on differentiation of self, differentiation of self-had a direct and significant effect on social interest and family function had a direct and significant effect on social interest (P<0.05), but relationship beliefs had no a direct and significant effect on social interest (P>0.05). Also, family function mediated by differentiation of self-had an indirect and significant effect on social interest (P<0.05), but relationship beliefs mediated by differentiation of self-had no an indirect and significant effect on social interest (P> 0.05). Conclusion: The results indicated the effective role of family function and differentiation of self in social interest. Therefore, to improve social interest can be improved the family function and differentiation of self.
