Sessler was born in Kraków, Poland in 1923. He was one of seven children. When he was aged 15, the entire Sessler family was sent to a concentration camp. According to Sessler, he eventually escaped and reached Russia, but the authorities sent him to Siberia. (One of his sons denied that this was true however.) Fortunately, as translators were needed, and Sessler spoke English, Polish, Russian, German and Yiddish, he was sent to London. Returning to Poland after the war, he found that many of his family were dead and that their home had been destroyed, so he decided to make a new start in New York.