Klein was born in Szatmárnémeti (present-day Satu Mare), in Partium--a region of Austria-Hungary at the time, it is now in Romania; he received his PhD at the University of Vienna in 1925.
Klein was born in Szatmárnémeti (present-day Satu Mare), in Partium--a region of Austria-Hungary at the time, it is now in Romaniato his parents Rabbi Yitzchok (Ignac) and Sarah Rachel (Roza) Klien nee Friedrich. He received his PhD at the University of Vienna in 1925.