Isidor Löwenthal was born in Bad Kissingen on February 17, 1880 as the youngest of five children of the tradesman Hermann Löwenthal and his wife Fanny, née Frank. He grew up with his parents in Promenadestrasse 3. When he was ten, he changed from Elementary School to Kissingen Realschule which his older brother Mayer had attended, too. In July 1896, he graduated there with good grades.

In 1910, he worked in Frankfort with the firm of Hermann Bodenheimer. Hermann Bodenheimer was married to Isidor’s older sister Nanny. In 1910, Isidor married Netty (Sheina), née Seligmann from Frankfort. The couple had two children. Only little is known about his further life. In the 1920s, he ran the firm “Isidor Löwenthal & Co” in Frankfort, which traded metal goods and also acted as an agent for mortgages and real estate. In August 1935, he lived in Friedberger Landstrasse 52 and left Frankfort in January 1939 (Information from Sigrid Kämpfer, Municipal Archive of Frankfort, mail from March 12, 2020). He obviously managed to emigrate to England with his wife, where he died in December 1959 at the age of 79. His wife outlived him by more than two decades, she died in January 1981 at the age of 90. Their daughter’s fate is unknown. Their son Hans who was born in 1911 had emigrated to Palestine and already died in Haifa in 1944 at the age of only 33.