Most existing literature treats family culture as a static and deterministic factor with a double-edged effect on the competitive advantage (CA) of family firms while overlooking its dynamic nature. Moreover, limited literature addresses how to solve this double-edged problem. This study fills these gaps by examining how family culture can generate sustainable CA from the lens of the affordance perspective. A three-stage process model is developed based on a longitudinal case study of Baiyun, a Chinese family firm with over a 100-year family history. This model suggests that family firms should intentionally adopt appropriate sensemaking and sensegiving strategies tailored to different stakeholders and dynamic entrepreneurship situations to effectively leverage the natural and designed affordances of family culture. By cultivating efficiency, emotional, and value identifications among internal and external stakeholders, these sensegiving strategies facilitate family collaboration, continuous trust, strategic focus, and extensive ecological synergy, which serve as the key sources of CA. Ultimately, the model emphasizes that the key to managing the double-edged effect lies in the four sensemaking strategies taken by family firm leaders. This study sheds light on the dynamic interplay between family culture, environment, strategies, and CA, offering actionable insights for family firms.