Differences in mortality among families give us clues about the importance of unobserved health-related behaviors. For example, if lower mortality was due to types of personal behavior learned in childhood, it should carry over to mortality at older ages. In this paper we use records from a nineteenth-century Belgian community to look at differences at mortality differences among families in two ways. First, we construct a direct measure of exposure to disease in childhood by counting the number of children in each family that died before age 15. Second, we calculate the overall effect of inter-family differences by using a "random effect" model that estimates the variance of the "family effect". Both of these measures show a strong family effect in childhood, but this effect diminishes after age 15 and disappears after age 55. Moreover, in a period still dominated by infectious diseases, those who survived diseases in childhood acquired immunities that helped them in later life.