Abstract
We examine how sibling gender composition affects high school educational outcomes, college major intentions, career aspirations, and academic self-confidence using large sample size cross sections of the Freshman Survey. We uncover some of the mechanisms explaining how opposite gender siblings produce negative academic impacts and increase stereotypical gender norm attitudes, particularly among girls. We complement the analysis with evidence from the Health and Retirement Survey as well as from the Panel Study of Income Dynamics and find concurring results. From there, we sketch the macro implications of the increasing proportion of brotherless girls over the last decades.