György was the son of Mihály Bethlen de Bethlen and Katalin Bornemisza de Petrelin. The date and place of his birth have not been found.
György Bethlen de Bethlen
Mihály Bethlen de Bethlen (-1656)
Katalin Thoroczkay de Toroczkószentgyörgy
Ilona Barlabási
Katalin Bornemisza de Petrelin