I wish everyone here the best. Life's tough whatever path you choose. None of us here can really offer up anything other than our feelings about this stuff.
The people saying they don't like kids so no thanks are missing the point. I don't like kids either, but my kids are fucking great. Partly because they're part of me and partly because of they start to annoy me I let them know and help them not.
What do you owe? Nothing, everything, it depends on your pov. Personally I wanted to experience what life is actually about, I loved being a child and I wanted to make the world better, making a good family with my wife seemed the way for me to do that. I couldn't miss out on what's to offer.
It just so happend to do all that and improve the lives of their grandparents. My kids report that they love their lives so alls good. Wife didn't want kids into her 30s and I was resigned to it. Realised just in time and I know for a fact it was the best choice she ever made.
None of this is to try to convince you, just to answer from my pov.
Evidentially. Obviously. That's not to say they cannot find fulfilment or a valuable life, but by it's very nature a life without children is less, in the same way that a life without a parent is definitively less. And it's up to him to rank happiness as he subjectively sees it, it's fine for him to think it's even reasonable given the data.
The reason for that is the you that chose that mother.
If having children isn't an opportunity for self reflection, it's nothing. Usually speaking you make a person with a person you choose and raise them within reason, how you see fit. How can any of that be someone else's fault.
You can say you could have known better what the woman was like, but probably should have known better is more accurate. Unless one is a simpleton, a victim. I don't like the victim narrative personally.
One can say it's all just an unceasing river of no free will. But that's not all the story. I don't think one has to feel bad about oneself now for making a poor choice in the past either. That was a different you. Recognising ones mistakes is part of preventing further ones.