We are also Viennese Jagendorfs. But we came to Vienna after 1918 from Buczacz in Galicia near Lemberg. My father's name was Chaim his father was Moshe. I know no brothers or sisters of Moshe who perished\ at dachau.
I think there was a Regen family in USA connected thru an Aunt called Golda. Back to Moshe Jagendorf, his children Nissan, Israel Mechel and Chaim. Nissan's daughter Dr Anna Igel died in California a few years agoa as did her husband more recenly Dr Leo Igel.
I am Chaim's only son and live in Jerusalem where I teach at the Hebrew University.