He is actually super concerned about having kids, as he's worried his "bloodline", might be viewed as a foreign element, and eliminated by "the world". And prevents him from intentionally forming any deep relationships, or feeling stable enough to commit to people/places/things. He views himself as a dead man walking.
Manga touches on this very lightly, I'm appreciative mangaka did at all to be fair. But WN spends a few paragraphs/chapters here and there talking about it as a recurring theme. He ends up settling on a platonic family dynamic, even once those "irregularity" concerns are addressed. I commented about this in an earlier chapter with WN quotes/citations.
I'm still waiting for him in the WN to overcome that hump and take responsibility to make some feral kittens.
