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Haylie Duff's famous younger sister is Hilary Duff. Hilary Duff is an American actress, singer, songwriter, and fashion designer. She rose to fame as a child actress in the late 1990s, starring in the television series Lizzie McGuire and in the films Cadet Kelly and Cheaper by the Dozen. In the early 2000s, she released a series of pop albums, including Metamorphosis, Hilary Duff, and Most Wanted.