TACOMA, Wash. — Prosecutors have charged two teen brothers accused in the violent murder of a boy whose remains were found in their home. Luis Arroyo, 16, on Monday pleaded not guilty to first-degree burglary and first-degree murder in the death of 15-year-old Hector Hernandez-Valdez. Arroyo, who has been charged as an adult, is being held on $2 million bail. Arroyo’s 14-year-old brother has also been charged with first-degree murder. A hearing was scheduled to determine whether the 14-year-old defendant will also be tried as an adult.