The major aim of the German TwinLife study is the investigation of gene-environment interplay driving educational and other inequalities across developmental trajectories from childhood to early adulthood. TwinLife encompasses an 8-year longitudinal, cross-sequential extended twin family design with data from same-sex twins of four age cohorts (5, 11, 17, and 23 years) and their parents, as well as their non-twin siblings, partners, and children, if available, altogether containing N = 4,096 families. As such, TwinLife includes unique and openly accessible data that allows, but is not limited to, genetically informative and environmentally sensitive research on sources of inequalities regarding educational attainment, school achievement, and skill development.