Francis II of France

Francis became King of France at fifteen in 1559 after his father Henry II died in a jousting accident. Though fourteen was the legal age of majority, his mother Catherine de' Medici handed power to the Guise uncles of his wife, Mary Queen of Scots, whom he'd married the year before. The Guises were Catholic hardliners, but they couldn't stop the Reformation tearing through Scotland, and the old alliance between the two kingdoms collapsed. Francis died of an ear infection on 5 December 1560, seventeen months into his kingship. Two of his brothers inherited the throne in turn, and neither could stop the religious wars that had begun to ignite under his name.