Victor Frankenstein describes William in the novel's first chapter:
William, the youngest of our family, was yet an infant, and the most beautiful little fellow in the world; his lively blue eyes, dimpled cheeks, and endearing manners, inspired the tenderest affection. (1.1.10)While Frankenstein is at Ingolstadt, Elizabeth provides this account of "darling William": "he is very tall of his age, with sweet laughing blue eyes, dark eye-lashes, and curling hair. When he smiles, two little dimples appear on each cheek, which are rosy with health. He has already had one or two little wives, but Louisa Biron is his favourite, a pretty little girl of five years of age" (1.5.5).
William is murdered by the Creature, who discovers that he is a relation of Frankenstein (2.8.9), and Justine Moritz is framed for the murder (1.6.10).