Arval Brothers (ärˈvəl) [key], in Roman religion, college of 12 priests chosen from the most distinguished senatorial families. It was said that the original brothers were sons of Acca Larentia. Theirs was chiefly an agricultural cult, but they were also concerned with the well-being of the imperial house. The Roman emperor was necessarily a member of the college. Their most important ceremony, held in May, was in honor of Dea Dia, a goddess of fields and crops.