Magnus, Duke of Östergötland Swedish prince; son of Gustav I of Sweden and Margareta Leijonhufvud (1542–1595) Parents Margaret Leijonhufvud Gustav I of Sweden Children Lucretia Magnusdotter Helena Gyllenhielm Siblings Princess Cecilia of Sweden Eric XIV of Sweden John III of Sweden Princess Elizabeth of Sweden Catherine Vasa of Sweden Charles IX of Sweden Anna of Sweden Princess Sophia of Sweden