Herman Loonstein was a son of Jacob Loonstein and Naatje Speijer. He married on 30 April 1924 in Arnhem to Sibilla de Jong, daughter of Meijer de Jong and Saartje Frankfort. The couple had 3 children: Nanny, Jacob Meijer (who both survived the Holocaust) and Sara.
City Archive of Amsterdam, archive card of Herman Loonstein.
In 1951 the Dutch Red Cross established that Herman Loonstein died between the twenty second of October 1943 (arrival in Auschwitz) and the first of April 1944 in Poland.
Dutch Red Cross