Complex sentence: In 1934, Jack and Irving Rosenthal, Brooklyn brothers and entrepreneurs who had built a fortune as concessionaires they rented umbrallas and owned a dance club/beer joint on the broadwalk.
Split into simpler sentences: In 1934, Jack and Irving Rosenthal, Brooklyn brothers and entrepreneurs who had built a fortune as concessionaires. They rented umbrellas and owned a dance club/beer joint on the broadwalk.