House of Lara
He was the son of Juan Núñez I de Lara "the Fat", head of the House of Lara, and his wife, Teresa Díaz II de Haro, Lady of Biscay. His paternal grandparents were Nuño González de Lara "el Bueno", Head of the House of Lara, and his wife, Teresa Alfonso. His maternal grandparents were Diego López III de Haro, Lord of Biscay and his wife, Constanza de Bearne. He was the great-great-grandson of Alfonso IX of León on both his mother's side and his father's side.