Complex sentence: The Adlers comprised the Jewish-American Adler acting dynasty, which had its start in the Yiddish Theater District and was a significant part of the vibrant ethnic theatrical scene that thrived in New York from the late 19th century to the 1950s.
Split into simpler sentences: The Adlers comprised the Jewish-American Adler acting dynasty, which had its start in the Yiddish Theater District. They were a significant part of a vital ethnic theatrical scene that thrived in New York from the late 19th century to the 1950s.