John III was the son of King Gustav I of Sweden and his second wife Margaret Leijonhufvud. He was the brother of Charles IX and Magnus Vasa and half-brother of Erik XIV. He was married from October 4, 1562 to Catherine Jagiellon (1526-1583), with whom he had a daughter Anna Vasa in addition to Sigismund, and from February 21, 1585 to Gunilla Johansdotter (Bielke) (1568-1597).
John III was the son of King Gustav I of Sweden and his second wife Margaret Leijonhufvud He was the brother of Charles IX and Magnus Vasa and half-brother of Erik XIV He was married from October 4 1562 to Catherine Jagiellon (1526-1583) with whom he had a daughter Anna Vasa in addition to Sigismund and from February 21 1585 to Gunilla Johansdotter (Bielke) (1568-1597)