Authorities say Roberto Aguirre Rojas has admitted to killing the boys, all under age 9, and his mother-in-law, Amelia Rivera Flores. The victims were found at the home of Rojas' in-laws, where they lived with the suspect's estranged wife.
Rojas' wife was critically injured in the attack. Authorities say she survived after her father came home and intervened.
The 45-year-old Rojas eventually turned himself in to sheriff's deputies.
Hidalgo County District Attorney Rene Flores told The Monitor in McAllen that he is seeking the death penalty. The trial was scheduled to begin Monday before state District Judge Aida Salinas Flores.