QUOTE: In brief, we find that children whose parents are married when they are born do better in life than those whose parents were not married when they were born. Children born to married parents are significantly more likely to be “on track” at every life stage than children who are born to unmarried parents.

https://ifstudies.org/blog/new-research-confirms-having-married-parents-helps-kids-get-ahead#

And so on, and so forth. You can google it yourself.