Half‑sibling decline simplifies families

Between 2013 and 2023 the share of U.S. children living in blended families fell from 23% to 17%, and much of that drop stems from fewer children living with half siblings (17% → 12%). This change appears tied to falling teen and very‑young adult births and fewer nonmarital multi‑partner childbearing, meaning family networks visible in households are becoming simpler on average. — Simpler household family structures reshape needs for custody law, child support tracking, school outreach, and social services because they change where children live and who is responsible for them.