Justin Mann was born in Bad Kissingen on August 26, 1903 as the oldest child of the butcher Lazarus Mann and his wife Cilly, née Löwenberger. He had five siblings. The family lived in Weingasse where Justin’s father ran a butchery.

Justin Mann, who attended Bad Kissingen Realschule from 1911 to 1917, saw himself confronted with an anonymous denunciation in his last year at school. The anonymous writer of the letter to the school complained about the – in his opinion - scandalous behavior of the young man and some of his fellow students who were 15 and 16 years old at that time: “Hereby, attention is drawn to the doings of some students of class 6. The way those young people behave is a real scandal. Not only do they attend performances in the theatre after 9:00 PM but they also visit the cafés of Bad Kissingen after the performances, which is at least at 10:30 or 11 PM, in the company of the actresses and and spend a lot of money there. It is also conspicuous that there are also big sums spent on flowers, for example on Saturday, 16. It can be said with certainty that these donations are worth a lot. / If you want to convince yourself, you yourself or the Beadle can observe it best after the end of a performance if you watch the students concerned. / Should there be no consequences, the attention of the local police should be drawn to it. / Several well-known gentlemen and ladies” (student’s file of Jack-Steinberger-Gymnasium).

Justin Mann apprenticed for the profession of a merchant after his time at Realschule and changed his place of residence very often in the following years. Between 1920 and 1933, he was in Frankfort, Ludwigshafen, Berlin, Warsaw and London, but for short intervals also in Bad Kissingen. Between November 1935 and May 1936, he lived in his hometown again before he went to Hamburg. The first ones to emigrate were his siblings Irene and Kurt who went to the USA. In July 1938, Justin and his mother went on board the ship “Georgic” in Le Havre and emigrated to New York where his brother Theobald (Teddy) was waiting for them. He had been living in New York since the end of 1934. According to US Census of 1940, Justin lived with his mother and the siblings Theobald (Teddy) and Kurt in a shared apartment in Manhattan. In October 1940 he was naturalized as an American citizen. The siblings Max and Luzie, however, became victims of the Shoa.

So far, nothing about Justin Mann’s further life is known.