US model-actress Riley Keough, the granddaughter of rock \'n\' roll icon Elvis Presley, is engaged to actor Alex Pettyfer, UsMagazine.com reported Tuesday. No details regarding when they got engaged or whether they have set a wedding date were immediately available. The couple met on the set of the soon-to-be-released film \"Magic Mike\" and have been dating for about six months, UsMagazine.com said. Keough is the 22-year-old daughter of Presley\'s only child, singer-songwriter Lisa Marie Presley. Pettyfer, 21, has appeared in the films \"I Am Number Four,\" \"Beastly\" and \"In Time.\"