Before the end of his reign, Stephen Držislav gave Svetoslav, his oldest son, the title of "Duke" and Svetoslav became his co-ruler. Držislav was preparing Svetoslav to be his successor. It is probable that Svetoslav ruled concurrently with his father during the 990s. Stone panels from the altar of a 10th-century church in Knin, reveal the following inscription in Latin: CLV DUX HROATOR IN TE PUS D IRZISCLV DUCE MAGNU. In English, this means: "Svetoslav, Duke of the Croats at the time of Drzislav the Great Duke ()". The stone panels are kept at the Museum of Croatian Archaeological Monuments in Split.