In Ofen in 1351, Margaret married Stephen, Duke of Slavonia, the youngest son of King Charles I of Hungary and Elizabeth of Poland.
Upon Stephen's death the same year, John inherited the duchy, with Duchess Margaret as his guardian.
[1] The Duchess remarried in 1356, choosing Gerlach von Hohenlohe as her second husband, but kept the regency over Slavonia, Croatia and Dalmatia.
However, a war broke out between the Kingdom of Hungary and the Republic of Venice in the spring of the same year and the royal court decided to end the duchy's autonomy.
John, who had been recognised as heir presumptive of both Hungary and Poland, died in 1360.