John I or John the Posthumous, 1316, king of France, posthumous son of King Louis X. He lived only five days and was succeeded by his uncle, Philip V. According to legend, a dying child was substituted for John, who was then brought up by a merchant in Siena. In the mid-1300s a Sienese named Giannino di Guccio became convinced that he was John I and trekked through Europe seeking recognition as the rightful sovereign.
See T. di C. Falconieri, The Man Who Believed He Was King of France (2008).
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