Stephen was the youngest of five sons born to Charles I of Hungary and his third wife, Elizabeth of Poland.

[2][9] Decades later, the Polish historian, Jan of Czarnków, claimed that Charles had decided to secure a throne for each of his sons and wanted to make Stephen his heir in Hungary.

[10] Next year, a Venetian envoy recorded that Charles was planning to visit Dalmatia along with his wife and "their younger son" who must have been Stephen.

[6] At Stephen's request, the judge royal, Paul Nagymartoni, deferred a hearing in 1343 and exempted a nobleman of paying a fine in 1344.

[6] Stephen was regularly mentioned in his brother's charters of grant from May 1345, evidencing that he had become a member of the royal council.

[17] Historian Éva B. Halász says, the establishment of Stephen's own household was most probably connected to his brother's negotiations with the papal legate, Guy of Boulogne.

[8][18] One of his retainers, Thomas Gönyűi, was first mentioned as the ispán (or head) of a Slavonian county already on 8 December 1349 and the ban of Slavonia did not witness Louis I's charters from the same month until October 1350, showing that Stephen received the realm in late 1349.

[21] Thereafter, Louis I appointed him to administer Croatia, Dalmatia and Slavonia, most probably because the relationship of Hungary and the neighboring powers, Venice and Serbia, had become tense.

[21] His relationship with his tutor had worsened for unknown reason and Ladislaus described Stephen as a new Nero in a letter addressed to the pope.

[15] Stephen married Margaret only after her father's death, in late 1350, because Pope Clement VI had sharply opposed the marriage.

[21] The Polish noblemen acknowledged Louis as Casimir III's sole heir in July 1351 only after he had promised that he would not allow Stephen to participate in the government of Poland.

[30] Stephen's son, John, inherited Croatia, Dalmatia and Slavonia from his father, but he was still a child when he died in 1360.