Sibling gaps reveal PGS family confounding

Comparing polygenic‑score prediction within sibling pairs versus unrelated individuals exposes how much of genetic prediction comes from shared family factors (ancestry, parental genotypes, socioeconomic environment) rather than an individual's own genome. Measuring the within‑family to population PGS ratio for cognitive and educational traits across childhood to early adulthood makes family confounding visible and quantifiable. — If within‑family PGS prediction is substantially weaker, policymakers and journalists should treat headline claims about PGS 'predicting intelligence' with caution and rethink uses in education, employment, and reproductive decisions.