Hungarian chronicles agree that Stephen's mother was Sarolt, daughter of Gyula, a Hungarian chieftain with jurisdiction either in Transylvania or in the wider region of the confluence of the rivers Tisza and Maros. Many historiansincluding Pál Engel and Gyula Kristópropose that her father was identical with "Gylas", who had been baptized in Constantinople around 952 and "remained faithful to Christianity", according to Byzantine chronicler John Skylitzes. However, this identification is not unanimously accepted; historian György Györffy states that it was not Sarolt's father, but his younger brother, who was baptized in the Byzantine capital. In contrast with all Hungarian sources, the "Polish-Hungarian Chronicle" and later Polish sources state that Stephen's mother was Adelhaid, an otherwise unknown sister of Duke Mieszko I of Poland, but the reliability of this report is not accepted by modern historians.