Complex sentence: He married Frieda Schiff, daughter of Kuhn, Loeb & Co. senior partner, Jacob Schiff, and Frederick Marcus, Gerald Felix, Paul Felix and Edward Mortimer Morris, who were sons of theirs, were all active in community service.
Split into simpler sentences: He married Frieda Schiff, daughter of Kuhn, Loeb & Co. senior partner, Jacob Schiff. Their four sons, Frederick Marcus, Gerald Felix, Paul Felix and Edward Mortimer Morris, were all active in community service.