Del Castillo was a rebellious youth, and on the instructions of his mother, in 1952 he joined the Mexican seminary for foreign missions in Mexico City and was a member of the Congregation of the missionaries of Guadalupe, priestly studies that he abandoned in 1953. Not knowing what to do with his life, Del Castillo thought about studying medicine.
Del Castillo, who was defiant, attended the Mexican seminary for foreign missions in Mexico City as a member of the Congregation of the missionaries of Guadalupe. He discontinued priestly studies in 1953 due to uncertainty about his future, considering medical education.