Your research isn't quite accurate about children being raised in single or co-parenting households. Many children thrive in them and there's little research on the damage a so-called "normal" family causes: https://omgchronicles.medium.com/is-divorce-really-worse-for-kids-than-a-normal-family-a57d1af501bc

Also, many people raise kids together without marrying:

https://omgchronicles.medium.com/why-all-women-need-renewable-marriage-contracts-1ce134c89890