Complex sentence: His formative years in Buffalo revealed him to be a boy of unusual intelligence and drive with a keen early interest in literature, his doting mother ensuring that her son had all the advantages of an upper-middle-class upbringing.
Split into simpler sentences: His formative years in Buffalo revealed him to be a boy of unusual intelligence and drive with a keen early interest in literature. His doting mother ensured that her son had all the advantages of an upper-middle-class upbringing.