kőszegi was born in 1282. sometimes after 1299, he became provost of the collegiate chapter of st. adalbert church in győr. 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. 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.