View gallery Image Credit: REX/Shutterstock Lyle and Erik Menendez have been serving life sentences for the brutal murders of their parents on August 20, 1989, when the brothers - then 21 and 18 - shot and killed José and Kitty Menendez inside their Beverly Hills mansion. More than three decades later, the Menendez brothers were thrown back in the spotlight as the focus of Monsters: The Lyle and Erik Menendez Story.