Establishing the fact of incapacity is both a legal and a clinical process, overseen by laws and professional standards that establish a requirement to consult with family and those closely connected to the individual whose capacities are being assessed. And yet the role played in this process by those ‘significant others’ has never been studied. The present article discusses the various representations of this role as seen by the professionals involved in the determination of a subject’s incapacity and of the suitability or unsuitability of the significant other to ensure the protection of the person lacking capacity. The way in which professionals perceive those significant others during the process of determining the subject’s incapacity is based on a judgment of the adequacy or inadequacy of the significant other to ensure the protection of the person lacking capacity. These representations are closely linked to the role played by the significant others throughout the process and can be broken down into three typical figures : 1) the contributor significant other; 2) the protector significant other and 3) the problem significant other.