Świętosława was the daughter of Duke Casimir I of Poland and his wife Maria Dobroniega of Kiev.

[1] She was related to the House of Přemysl, the family of her future husband, through her great-grandmother Doubravka of Bohemia.

In addition, Vratislaus demonstrated friendly relationships with Boleslaus II the Bold, but at a later date they disputed the Czech-Polish borders.

[1] Her sons Vladislaus and Soběslav became dukes in the unquiet years after the death of their father, while her daughter Judith was married to Wiprecht, his ally and friend.

[2] Świętosława, who was a widow for thirty years, lived to see the victory of her son Soběslav in the Battle of Chlumec and died in September 1126.