 Dueñas was born on March 19, 1911, to his parents of Luis Paulino Dueñas and Josefa Martínez Baza in Hagåtña, Guam, with siblings Pedro, Eduardo, among others.Dueñas studied for the priesthood in Manila, and became the second Chamorro Catholic priest when he was ordained in 1938.During the World War II Japanese occupation of Guam, Japanese forces who suspected Dueñas of knowing the whereabouts of a fugitive American serviceman tortured and, on July 12, 1944, killed him.