Hello, Valentin. I'm pretty certain that Simon Rothstein had a sister named Dorothea.  I stumbled upon this biography of someone named Lotte Kallenbach-Greller, maiden name Karoline Greller. The text notes that "Karoline Greller's parents were the merchant Nathan Greller (died 1947 at the earliest) and Dorothea Greller, née Rothstein (born on July 20, 1871, died 1947 at the earliest)."  (Google Translate from the German)

The text quotes Kallenbach-Greller from 1946:
“I was born on March 22nd, 1893 in Sadagòra, Bukowina - until 1918 crown land] of the Austro-Hungarian monarchy - as the daughter of Jewish parents of the Mosaic faith. Shortly before I was born, my father, Nathan Greller, emigrated to America together with my mother's brother, Simon Rothstein, because of poor economic conditions, where they both established a respected existence as merchants. Both still live in New Jersey as American citizens." 

Along with the place of birth, Simon Rothstein lived in New Jersey so this is almost certainly him, but Kallenbach-Greller does not mention other brothers of her mother. How did you access the Czernowitz vital records?
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Scott Rothstein