Having children fundamentally changes you, mentally. What may not have been a priority before, suddenly becomes a terminal value in itself once you bond with a little one. This is definitely something hard-wired into brains by evolution--ask any parent about their experience!
I think you're probably right about this (not based on first-hand experience of having a child, mind - I haven't), but I can't quite see what it's doing here. Is this meant to be some sort of objection to the comment you're replying to? It isn't obviously in tension with it.
There is a lot of research on this topic. I know later studies contradict earlier studies, but I'm not sure who to believe here. Wondering if anyone can help.
In case it isn't clear, the basic question is the effect of having children on happiness.