Why did Lyle and Erik Menendez kill their parents? Updated: Apr 7 2021, 11:20 ET LYLE Menendez and younger brother Erik are serving life sentences for the 1989 murder of their parents. 5 Why did Lyle and Erik Menendez kill their parents? The legal team for Lyle and Erik Menendez argued that they were sexually abused by their father. The brothers claimed the fatal shooting of Jose and Kitty Menendez in their Beverly Hills home was a form of "imperfect self-defense," according to The New York Times. They believed, "honestly though mistakenly," according to the newspaper, that their parents were going to kill them if they did not act.