Subjective life expectancy is a powerful predictor of a variety of health and economic behaviors. This research expands upon the life expectancy literature by examining the influence of familial health histories. Using a genetic/environmental model, we hypothesize that individuals’ assessments of their life expectancies will be linked to the health of first-degree and second-degree relatives, with same-sex relatives’ health exercising a stronger effect than that of opposite-sex relatives. Multivariate analyses based on data from a 2009 survey merged with familial health records (N = 1,019) confirm that the health experiences of same-sex, first-degree relatives are linked to respondents’ subjective life expectancy. The relationship between the health experiences of second-degree relatives and subjective life expectancy is much less pronounced. These findings have the potential not only to inform our understanding of health behaviors but also to encourage communication between patients and health professionals aimed at promoting preventative behaviors.