Complex sentence: He married Barbara Yelverton, a daughter of Admiral Sir Hastings Reginald Yelverton, by whom he had three children, the youngest of whom, Giles Yarde-Buller, died of pneumonia at Lupton House in 1900, aged 24.
Split into simpler sentences: He married Barbara Yelverton, daughter of Admiral Sir Hastings Reginald Yelverton. They had three children, the youngest of whom, Giles, died of pneumonia at Lupton House in 1900, aged 24.