During the end of 1944 his grandfather lost his life during the siege of Budapest. Then his father, older brother and himself were arrested by the conquerors and sent in a concentration camp approximatively 45 miles East of Budapest. An infectious illness spread in the camp and his brother and father died but Ákos survived. He is a member of the group of five students of the late professor Lipót Fejér who called them "The Big Five". Four members of the group are retired mathematics professors in North America and only Császár became a university professor in Budapest.