The art and frame dealer Josef Isidor Landsberger was the second eldest of the eight children of Alexander (Samuel Abraham) Landsberger and Franziska, née Preisler, who came from Domausnitz (Sobotka) in Bohemia. The founding of the family business in Vienna dates back to 1833. Josef Isidor Landsberger's grandfather Isidor (1801-1865), who came from the then Hungarian city of Bratislava, and his father Alexander (1842-1917), who was also born in Bratislava, had been master gilders. Alexander Landsberger had also traded in paintings of saints and papal portraits as well as mirrors in his business at Lerchenfelderstraße 22 in Vienna’s 8th district. In 1899, Josef Isidor Landsberger took over the family business and was authorised to trade in gilded goods; in 1910, a trade licence for trading in pictures and frames was added. In 1919, the location of the unrecorded, export-orientated art and frame shop J. Landsberger (‘Gemäldehaus und Stilrahmenatelier’) was moved from Alserstraße 65 in Vienna’s 8th district, to Favoritenstraße 68 in Vienna’s 4th district. Josef Isidor Landsberger, who had converted to Protestantism in 1904, returned to the Jewish community in 1919. From his marriage to Irma Grünwald (1874-1916) in 1901 came his son Leopold Fritz, born in 1902, and from his second marriage to Irene, née Grün, also Jewish and born in Moravian Ostrava in 1890, came his daughter Franzi Irma (later Frances Pearson), born in 1921. Two of Josef Isidor Landsberger's brothers, Otto, born in 1874, and August Landsberger, born in 1879, were academic painters, while his brother Wilhelm, born in 1872, was a master gilder in the 8th district. Josef, who was responsible for the company's bookkeeping, and Irene as well as Leopold and Franzi Landsberger lived at Starhemberggasse 29/11 in Vienna’s 4th district, until the annexation of Austria to the National Socialist German Reich. In an export application to the Central Office for the Protection of Monuments from the beginning of February 1938, Leopold Landsberger registered 299 oil paintings for export in the name of the company, with himself listed as the recipient with a hotel address in London.

In July 1938, Josef Isidor Landsberger fled to Great Britain. An export application for 25 oil paintings for personal transport to ‘England - Sweden’ dates from the same month. Applications from his parents and the company from the same year concerned both removal goods and shipments to people and companies in various European countries and the USA. In his Declaration of Assets (VA) completed at the end of June 1938, Josef Isidor Landsberger valued his company at approximately 12,100 Reichsmarks and stated that it was already clear at the end of April that his business would have to be closed down due to the lack of a buyer. By December, his assets had been reduced by 8,700 Reichsmarks due to the closure of the business, bad debts, living expenses for his family, support for needy relatives and medical expenses. Josef Isidor, Irene and Franzi Landsberger left Vienna in December 1938, while Leopold Landsberger had already been living in the USA since October 1939, where his parents were to follow him in April 1944. The business licence of the J. Landsberger company expired in February 1939 ‘in accordance with the provisions on the elimination of Jews from German economic life’. In February 1939, the Property Transaction Office (VVSt) appointed Otto Faltis as the final liquidator of the closed business, and a liquidation surplus of just twelve Reichsmarks was achieved. In April 1941, Karl Ebner, the head of the "Jewish Department" of the Vienna Gestapo, issued a seizure order for the entire assets of Isidor, Irma and Franzi Landsberger, which were ultimately forfeited in favour of the German Reich in accordance with the 11th Ordinance to the Reich Citizenship Act of 25 November 1941. The Viennese lawyer Stefan Lehner acted as trustee.

Josef Isidor - now Joseph - and Irene Landsberger, who settled in the Manhattan borough of New York City and acquired US citizenship, were no longer able to earn a living due to their age and failing health and had to be supported by their children. Joseph Landsberger died in 1957 and was buried in the Beth El Jewish cemetery.