Besides his father-in-law, Kahn's other partners included Jacob Schiff, himself the son-in-law of Solomon Loeb, who co-founded the firm, and Paul and Felix Warburg. Almost immediately, Kahn was thrown into contact with railroad builder E. H. Harriman. In spite of sharply defined differences in temperament and method, they became as brothers. In opposition to Harriman's gruff, domineering, aggressive manner in business, was Kahn's calm, good-humored, almost gentle deportment. Kahn, although only 30 years old, took an almost equal part with Harriman in the gigantic task of reorganizing the Union Pacific Railroad, a work which in its early stages had been handled by Schiff. Kahn proved his ability to analyze mathematically and scientifically the problems that were constantly presented.