This study presents the development and validation of the Family Collective Psychological Ownership Scale (FCPO-S), an innovative instrument designed to measure the shared sense of ownership that family members feel toward their business. This scale captures two critical dimensions: family firm identification and interdependence, which reflect the emotional and strategic connections of family members to the enterprise. By focusing on these socioemotional aspects, the FCPO-S underscores the unique dynamics of family firms, where collective commitment and emotional ties can serve as significant competitive advantages. This scale constitutes a valuable contribution to business research, providing significant practical implications for understanding and managing the socioemotional dynamics of family firms.