Born in Prague, John was the third son of Emperor Charles IV (1316-1378) from his fourth marriage with the Griffin princess Elizabeth (c.1347-1393), daughter of Duke Bogislaw V of Pomerania.
In 1385 King Wenceslaus consigned him administration of Brandenburg, then formally under the rule of John's half-brother Sigismund and given in pawn to their cousin Margrave Jobst of Moravia three years later.