Going off the very little amount we have about Miroku's father and grandfather my poor brain decided to cook up Miroku's dad raised him with as much love and care he could give him because he himself was raised as a weapon, as an instrument of vengeance. From what Buddhism stuff I've read and the influence of Confucianism brain decided Mirkou's dad maybe forgave/understood his own father's faults and felt honor bound not just out of filial piety but as a duty of someone with spiritual power that the quest to end Naraku must be continued.
Or other option compartmentalised the fuck outta himself along with Naraku's gotta be slain somehow.
Either way he was not prepared to confront how small new humans are, nor how helpless they are, or feel loss and some anger about how he was raised so he resolves to give little Miroku as much love as he can. Raise him to fight and survive of course but be encourage him with care and not despair disguised as wrath. Near the end maybe he worried that a gentler raising was selfish on his part and was even a little afraid that having his son love him will make his death hurt more than his own father's death hurt him.
I'm running out of articulateness but like if he was raised weapon-y Miroku's dad might not have had good social skills etc. But Miroku himself has enough social skills and social intelligence to make friends, allies, and con the fuck outta people.
The part that made this hot dog roll around in my brain at enough speed to need freeing is the concept of being raised with kindness instead of an an instrument of vengeance helped defeat the being of abject cruelty that was Naraku. Power of love in multiple forms.
