Complex sentence: Felix M. Warburg and his brother Paul Warburg were international German bankers in the early 20th Century who cultivated their fortunes at the New York banking firm Kuhn, Loeb, & Co. Felix married Freida Schiff, daughter of Jacob Schiff, a partner at the firm.
Split into simpler sentences: Felix M. Warburg and his brother Paul Warburg were international German bankers in the early 20th Century who cultivated their fortunes at the New York banking firm Kuhn, Loeb, & Co. He married Freida Schiff, daughter of Jacob Schiff, a partner at the firm.