Data from historical populations provide an excellent context for examining the familial and environmental components of survival to old ages. Using data from the Registre de population du Québec ancien produced by the Programme de recherche en démographie historique of the University of Montreal, we investigated the relation between the survivorship of individuals and the longevity of their siblings, their parents and their spouses in a population of French-Canadian colonists born between 1625 and 1704. We also introduced factors to take account of environmental and social conditions. We used the average age at death of siblings surviving past age 50 and simulated the “sibling” effect that was not influenced by sibship size. Using Cox proportional hazards models, we found a highly significant sibling effect. Each additional year in average age at death of siblings reduced the risk of death by 2.1% for males and 1.6% for females. There is also some evidence that shared social and environmental conditions, both in childhood and in adult life, influence this relationship.