John was born into the Forgács branch of the wealthy and prestigious "gens" (clan) Hont-Pázmány around 1240. The ancestors of the kindred, Swabian knights Hont and Pázmány arrived to the Principality of Hungary in the late 10th century, according to the chronicle of John's contemporary Simon of Kéza. John's father was Andrew, who erected castles near Turóc and Gímes (present-day Kláštor pod Znievom and Jelenec in Slovakia, respectively) following the First Mongol invasion of Hungary. He was a faithful confidant of Béla IV, then Stephen V. Andrew served as count of the tárnoks (financial officials) from 1249 to 1256, and "ispán" of Bánya (Árkibánya) ispánate on several occasions, which laid in the territory of Nyitra County. John's mother was Maria Nánabeszter.