Complex sentence: His only child, Maude Cassel (1879--1911), also died young, he doted on the two granddaughters she left him, especially the eldest, Edwina, who looked after him in his old age.
Split into simpler sentences: His only child, Maude Cassel (1879--1911), also died young. He doted on the two granddaughters she left him, especially the eldest, Edwina, who looked after him in his old age.