In the first part of this study I aim to describe the development of the popular story of the conception of James I of Aragon (1213-1276) from the time of the king’s own chronicle until the seventeenth century. In the second part, I deal with the actual historical context of the king’s conception, which, given the well-known antipathy between his father, Peter II (1196-1213) and his mother, Marie of Montpellier, is in its way no less remarkable than the stories told by later chroniclers and in the theatre. In the third part of the study, I tentatively suggest the reasons - political, religious, social, cultural and artistic - why the story developed in the way that it did.