Complex sentence: The anti-Semitism experienced by and motivating Harold Abrahams was exaggerated in the film; it was apparently mainly a desire to outdo his older brothers, one of whom, Sidney Abrahams, was a 1912 Olympian, that motivated him.
Split into simpler sentences: The anti-Semitism experienced by and motivating Harold Abrahams is somewhat exaggerated in the film. In addition, a desire to outdo his older brothers, one of whom, Sidney Abrahams, was a 1912 Olympian, motivated him.