Benedict was born into an unidentified family from
Zala County, whose nobility was confirmed shortly after the
First Mongol invasion of Hungary. According to 19th-century clerical historian Antal Pór, he belonged to the
gens Nádasd (ancestor of the wealthy
Nádasdy family), while Mór Wertner identified him as a member of the
Lőrinte kindred, but other historians do not share either viewpoints. Benedict had three brothers, Dedalus,
ispán of Zala County (1273–1274), Beke and Stephen. When
Atyusz V Atyusz was charged disloyalty by
Ladislaus IV of Hungary, the king donated the Szentmiklós Castle and its surrounding villages to them in 1276, not long before Benedict's death. In contemporary records, his name is referred to with the honorary title of "
magister", demonstrating his education and skills in science. He first appears in sources in 1255–56, when participated in determination of a border along the
Drava on behalf of
Béla IV of Hungary. He started his ecclesiastical career in the
Diocese of Pécs. Soon, he joined the court of the king's eldest son
Duke Stephen, where he was mentioned as a notary in 1257. Stephen attained the
age of majority in that year and became
Duke of Transylvania. Two years later, he was appointed
Duke of Styria, which he governed with the help of local lords and bureaucrats, who originated from near the Austrian border. Benedict elevated into the position of vice-chancellor in the ducal court by 1259, while he was also titled provost of
Friesach and archdeacon of Valkó, which belonged to the
Diocese of Veszprém. After Béla IV was forced to renounce of Styria in favor of
Ottokar II, Stephen returned to
Transylvania and started to rule it for the second time after 20 August 1260. Benedict escorted his lord to the eastern province and retained his position of vice-chancellor. He was styled as provost of
Szeben (today Sibiu,
Romania) from 1261 to 1262, then as
provost of Arad since 1262. He held the latter clerical dignity until the end of 1273. Stephen's relationship with Béla IV deteriorated by the early 1260s. After a brief civil war between them, Benedict of Szeben mediated the reconciliation between father and son at
Pressburg (present-day Bratislava, Slovakia) in the autumn of 1262, alongside other prelates. Initially, Benedict remained loyal to the duke, but just before the emerging
civil war between father and son, he escaped from Transylvania and defected to the royal court not long before October 1264. He was replaced as vice-chancellor by
Lodomer still in that year. It is possible that Benedict actively participated in the conflict with his troops, as two of his
familiares, brothers Simon and Synke were granted a land in Zala County in April 1265 by Béla for "their loyalty in various military campaigns". When Stephen V succeeded his father as
King of Hungary in May 1270, Béla's numerous partisans were forgiven, including Benedict, who took the role of royal vice-chancellor immediately after the death of the old monarch. He held the dignity until the sudden death of Stephen V in August 1272. In the summer of 1270, Benedict also acted as envoy sent to the Bohemian court, alongside
Bás Mezőpilis. They met the envoys of Ottokar in
Brno to conclude a truce. They informed
Philip of Spanheim, Stephen's ally, on the truce on 2 July 1270. In August 1271, after Ottokar II invaded the lands north of the
Danube and destroyed the archives of the
Diocese of Nyitra (Nitra), Benedict, alongside vice-
ispán Michael and
Sixtus of Esztergom, were mandated by Stephen V to determine the borders of the diocese, cataloging its existing estates and churches. When Bishop
Lampert Hont-Pázmány requested the monarch to transcribe and confirm his father's privilege letter for the
Diocese of Eger in 1271, Benedict represented the king in the committee, which was sent to the bishopric to examine the documents and boundaries. Benedict was also a member of that delegation which was sent to
Marchegg following the Bohemian–Hungarian war in 1271. ==Archbishop-elect==