Many childless men already say that it is bad to date or marry a single mom for some key reasons( like having to face her ex) and if the relationship /marriage ends they are at risk to being sent to court and be legally ordered to pay child support for children that aren't his. That may be very humilliating for a man. It van happen to women but it is far more likely to happen to men as most single parents are women.

This is called parenthood by stoppel. I have heard about some cases which the boyfriend of a single mother( they had a short relationship) or a stepfather were ordered by family judges to pay child support because of affectiveness between them and the kids and the courts just wanted to meet the children's rights. And there are threads about this here in Reddit.

If it is a long lasting relationship it makes sense. Let's say I met a single mom with a small child and we love each other and we marry.( I am single and childless anyway) Since we live together she would probably expect me to do parent duties even if I am not their biological father. As years passes the child recognize me as their dad and I would also consider them my kids. If I and my wife divorce after several years of marriage then it would seem bizarre to just disappear from the child life without any responsibility since I helped to raise them.

But I have seem cases that a man was ordered to pay child support even after they had a short relationship like a few months or an year( they were not married). Then it does not make any sense.

Have to pay child support for another person's child without having feelings for them is a scam

The dangers of dating single moms

Deste a single Mother may make you legally have to pay child support

Never date a single mother in the United States