In one breath you say children from nuclear families do better,
Successful nuclear families (28%?) with mom and dad raising their biological children.
The failed or broken home nuclear families don't get counted, such as single moms, divorces, step parents, adoptions, foster families ...
The nuclear family is great when you only count the successes.
All the extended families get counted. Due to do social mobility, the system is unintentionally rigged against the extended family. Also, the extended family tends to be the safety net for the failed nuclear family.