Scholars have dated Marie's works to between about 1160 and 1215, the earliest and latest possible dates respectively. It is probable that the "Lais" were written in the late 12th century; they are dedicated to a "noble king", usually assumed to be Henry II of England or possibly his eldest son, Henry the Young King. Another of her works, the "Fables", is dedicated to a "Count William", who may have been either William of Mandeville or William Marshall. However, it has also been suggested that Count William may refer to William Longsword. Longsword was a recognized illegitimate son of Henry II. If Marie was actually Henry II's half-sister, a dedication to his son (who would be her nephew), might be understandable.