Complex sentence: Holbrooke's father, a doctor who died of cancer when Richard was 15 years old, was born of Russian Jewish parents in Warsaw and took the name Holbrooke after migrating to the United States in the 1930s.
Split into simpler sentences: Holbrooke's father was a doctor who died of cancer when Richard was 15 years old. The elder Holbrooke was born of Russian Jewish parents in Warsaw and took the name Holbrooke after he immigrated to the United States in the 1930s.