Engaged: Miley Cyrus, 19, and Liam Hemsworth, 22, her Australian actor beau of three years, their reps told People Wednesday. Which Hemsworth is he? The one from “Hunger Games”; it’s his brother Chris who plays Thor in “The Avengers.” Too young? Chill out: The Disney Channel veteran/pop star is already more than a year older than Elizabeth Taylor at the time of her first marriage, and almost as old as Princess Diana. She’ll be fine. Three-and-a-half carat ring. No wedding date yet announced.