The interpretation of drawings made by school-age children is a classic study field in child psychology. Yet clinical psychologists and researchers in psychology have concentrated more on analysing the semiotic value of a drawing made by the child. The authors of this paper offer an original approach to this graphic realisation, which consists of simultaneously calling upon two siblings and filming this collaborated production of a drawing of the family. Through the example of the negotiation about the parents' sizes, the authors underline the relevance of the filming which enables them to grasp the story of the drawing as a dynamic production, in which the divergences in representations and the interactional process underlying this construction are revealed. (Contains 2 figures and 7 notes.)