ESON. Aeson, king of Thessaly, was Jason's father. His brother Pelias drove him from the throne, exiled his family, and ruled in his stead. When Jason appeared with only one sandal, Pelias recognized him as his brother's son and sent him in search of the Golden Fleece, hoping that he would die in the search and never return (Met VII.84, 162-293; Guido delle Colonne, HDT I-III).
Eson is Pelleus's brother; when he becomes too old to govern, he gives his kingdom to Pelleus, LGW 1396-1405. This different version of the story appears in Ovide Moralisé VII.1-193. Chaucer omits Medea's rejuvenation of Eson from his version. [Guido: Jason: Medea: Pelleus]