In أَكَلَ الْوَالِدُ وَالْأَبْنَاءَ, what is the role of الْأَبْنَاءَ?

Maf'ul Ma'ahu: The Accompanying Noun

• It is the verb
• It is the only subject
• It is mudaf ilayh
• It is the mansub maf'ul ma'ahu