While recent research finds strong evidence that birth order affects outcomes such as education, IQ scores, earnings, and health, the evidence for effects on political outcomes is more limited. Using population-wide data from Sweden, our within-family estimates show that firstborns are significantly more likely to run for and be elected to political office. In addition, for the males in our sample we test whether a number of potential mechanisms account for the relationship between birth order and political participation. Disconfirming our expectations, the birth order effects are only marginally smaller when controlling for occupational economic status, cognitive ability, and leadership skills. Our results suggest that big brother, or for that matter big sister, not only sees us; to a certain extent he or she also rules us.