Demetrius Zvonimir married Helen of Hungary in 1063. Queen Helen was a Hungarian princess, the daughter of King Béla I of the Hungarian Árpád dynasty, and was the sister of the future Hungarian King Ladislaus I. Zvonimir and Helen had a son, Radovan, who died in his late teens or early twenties. King Demetrius Zvonimir died in 1089. The exact circumstances of his death are unknown. According to a later, likely unsubstantiated legend, King Zvonimir was killed during a revolt in 1089.