The sibling effect: how birth order subtly steers kids—and what helps level the playing field

New research suggests birth order affects life outcomes more through family dynamics and resources than fixed traits. Younger siblings often benefit from parents who are wealthier and more experienced than with their first child, while older siblings can act as mentors and rivals, shaping opportunities and motivation. The piece notes patterns such as more younger siblings in elite athletes and discusses how parents and policymakers can help close gaps by supporting early education, mentoring, and resource access for firstborns and other children.