Complex sentence: Rabban's descendants continued to exercise dominion over the Jews of the Malabar coast until a conflict broke out between one of his descendants, Joseph Azar, and his brother in the 1340s.
Split into simpler sentences: Rabban's descendants continued to have prominence over other Jews of the Malabar coast for centuries. A conflict broke out between descendants, Joseph Azar, and his brother in the 1340s.