Rezső was born in October 1863 in Kőszeg and his baptism took place there on October 4th, 1863.1 Rezső's father was Miklós Nagy and his mother was Alojzia Szluha. His paternal grandparents were Antal Nagy and Anna Balogh. He had two brothers and a sister, named Ádám, Adorján and Margit. He was the second youngest of the four children.