Mr. Warburg, a brother of the late Felix M. Warburg, was for nearly fifty years the head of the four-generation-old German banking house of M.M. Warburg and Co, until it was taken over by the Nazis.

Paul Felix (“Piggy”) Warburg, 35, urbane, waffle-cooking nephew of the late Paul M. Warburg, a founder of the Federal Reserve System, became a partner in the Manhattan brokerage house of ...