Stephen Estaban Kelen completed his matriculation in Budapest and studied Philosophy at Karlovo University in Prague, Czechoslovakia. Later he obtained a Diploma from the British Association of Industrial Editors. He began writing in Hungarian, then Czech and finally in English. From the age of 17 he published in leading Hungarian newspapers.
He travelled in New Zealand, Asia, Africa, South America and Tristan da Cunha before settling in Australia. In 1939 he volunteered for the Australian Army serving, for seven years, in New Guinea, the Halmaheras, North Borneo and, finally, as a member of the British Occupation Forces in Japan. In Japan he was transferred from the 66th Australian Infantry Battalion (Intelligence) to BCON, the British Commonwealth Occupation Newspaper, and was one of its top feature writers. He worked alternately in Kure, Osaka and Tokyo.
During the 1940s and 1950s, while working as an author and journalist with Radio ABC, he wrote many documentaries and features on topics including industry, current affairs, history, music, religion and literature and also dramatised book reviews, plays and short stories. From 1960 to 1977 he worked with Goodyear as a managing editor.
Kelen was named a life member of the Australian Journalists Association and of International PEN (of whose Sydney branch he was President from 1975 to 1985). He held membership of The Australian Society of Authors, The British Association of Industrial Editors and the International Association of Business Communicators USA; he was also an Associate Member of the Société des Auteurs et Compositeurs Dramatiques.
Kelen received several awards for literature. His short story, The Olympic Runner, won a prize in the 1948 Sun-News Pictorial Short Story Competition. In 1965 his play, Shadow of the Crabbe, won the Warrandyte Arts Association Drama Group Original Australian Play Competition and another, Illicit Petting, was shortlisted in the 1988 Manly Bicentennial Literary Contest. In 1983 he was named Gold Medal Champion of Hungary in Perpetuity. He is the father of Christopher Kelen and S. K. Kelen (qq.v.)