This paper estimates family spillovers in high school major choice in Sweden, where admission to oversubscribed majors is determined based on GPA. Using a regression discontinuity design, we find large sibling and intergenerational spillovers that depend on the gender mix of a dyad. Same-gender siblings copy one another, while younger brothers recoil from older sister's choices. Fathers and mothers influence sons, but not their daughters, except when a mother majors in the male-dominated program of Engineering. Back of the envelope calculations reveal these within family spillovers have sizable implications for the gender composition of majors.