The analysis of the parish records of Belén bring us closer to the demographic reality of the Altos de Arica in the late colonial period, where high rates of legitimacy and the low percentage of children per family are aspects that stand out. This data gives new perspectives from which to address the demographic history of indigenous families in Latin America. Demographic results obtained through from the French method known as "family reconstitution", relating to the family life of sixty-nine marriages from the village of Belén, lead us to propose three factors that may have affected the low percentage of children: infant mortality during pregnancy and childbirth, possible mechanisms of birth control and a high mortality of parents.