Sybille of Cleves

Sybille of Cleves ({ _de. Sibylle von Jülich-Kleve-Berg}) (January 17, 1512, Düsseldorf—February 21, 1554, Weimar) was the eldest daughter of John III, Duke of Cleves and a sister of Anne of Cleves. Sybille's mother was Maria of Jülich-Berg (1491-1543). In September, 1526 Sybille married John Frederick I, Elector of Saxony. She had four sons with her husband: Johann Frederick II, Duke of Saxony (b. Torgau, 8 January 1529 - d. as imperial prisoner at Schloss Steyer, Upper Austria, 19 May 1595);
Johann Wilhelm, Duke of Saxe-Weimar (b. Torgau, 11 March 1530 - d. Weimar, 2 March 1573); Johann Ernst (b. Weimar, 5 January 1535 - d. Weimar, 11 January 1535);
Johann Frederick III, Duke of Saxe-Gotha (1554-1565) (b. Torgau, 16 January 1538 - d. Jena, 31 October 1565). During the siege of Wittenberg, Sybille was protecting it in her husband's stead. To save his wife and sons, and to prevent Wittenberg from being destroyed, John Frederick conceded the Capitulation of Wittenberg, and, resigned the government of his country in favor of Maurice of Saxony.