When Réthy was born, his parents had to leave their home country because of the 1956 Hungarian Revolution. They emigrated to Brazil where they stayed until they went to Germany in 1968. Réthy obtained his "Abitur" certificate so he was able to attend Johannes Gutenberg University of Mainz where he studied literature and journalism. In the meantime he worked in the sports archive of the ZDF and became a freelancer later. Since 1987, he has been salaried.