[1] Genealogist Pál Engel placed his name on the family tree as the son of Ivan's brother, another powerful oligarch Henry Kőszegi, but without explanation and reference.

[3] Excluding Gregory due to estimate age, Nicholas' biographer Ádám Vajk argued his diocese laid in the territory of Ivan Kőszegi, who ruled Western Transdanubia at the turn of the 13th and 14th centuries.

[6] He was styled as magister, when held the office of vice-chancellor in 1307 in the court of Otto of Bavaria, one of the pretenders to the Hungarian throne after the extinction of the Árpád dynasty.

[5] The career advancement of Kőszegi was due to his family influence and wealth in the region, who de facto ruled their province independently of the royal power by then, and intended to acquire the church lands to extend their dominion in Győr and Sopron counties.

Contemporaries, including papal legate, Gentile Portino da Montefiore did not question the legitimacy of his election in the upcoming years, albeit it could be a sign of political flexibility.

[12] Thereafter, Pope Clement V confirmed his election on 28 July 1310,[7] describing Kőszegi as solutus and soluta, i.e. natural son of free and unmarried men, a 28-year-old clergyman.

Bishop Nicholas stayed away from the conflict; he was present at the siege of Komárom in November 1317, when Charles I successfully seized the fortress from Matthew Csák.

[18] After Charles neglected to reclaim Church property that Matthew Csák had seized by force, the prelates of the realm, including Kőszegi, made an alliance in Kalocsa in March 1318 against all who would jeopardize their interests.

[20] It is presumable that Charles took into account the fort's strategic importance against Matthew Csák and its bishop's disloyal and rebellious kinship, when made the decision.

[22] Kőszegi protested against the step at the papal court, without success, despite that Pope John XXII even appointed conservators, bishops Lawrence of Vác and Henry of Veszprém, and Matthias, Provost of Győr in order to defend Nicholas' interests in November 1318.

Accordingly, he transuded private information to the Holy See about the bishop's parentage, in order to turn him out of office, and occupied Szombathely and other bishopric estates in Vas County.

Kőszegi and Nicholas Dörögdi represented the interests of the archbishop, while Csanád Telegdi and John, archdeacon of Hont were appointed as trustees of Henry.

[27] Kőszegi was appointed conservator (defender) to the Archdiocese of Salzburg along with Pagano della Torre, Patriarch of Aquileia and Rudolf von Montfort, Bishop of Constance in April 1331.

[26] Upon the instruction of Pope John XXII, Nicholas Kőszegi investigated the circumstances of the election of Thatamerius, the provost of Székesfehérvár in June 1331, along with the papal tax collectors present in Hungary.

The papal court ordered Kőszegi to recover the confiscated possessions and revenues of the Cistercian Klostermarienberg Abbey (Borsmonostor, today part of Mannersdorf an der Rabnitz, Austria) and to settle and mediate the dispute between the parish of Debrecen and the local Dominican friars.

[30] In addition to his servitium commune, the sustenance of papal legate Gentile's court in the first years also increased Kőszegi's expenditures, who, compared to other bishops, contributed significantly to this because of his temporary, unstable political status.

[32] Kőszegi had several conflicts and lawsuits with the town of Sopron in the upcoming years; he contested the determined borders between Págya and Fertőrákos, while he was also charged that unlawfully occupied Meggyes (present-day Mörbisch am See in Austria) from the burghers.