It's hard to say who the younger siblings/relatives will be related to, but I see another good aspect to the introduction of new side characters who are unambiguously too young to be sexualized.
This will give the MC a chance to see some of the women in his harem/his circle that will join his harem with younger family members (cousins/half-siblings).
He will get a sense of the way they interact with younger children and perhaps see a more unguarded version of some of the women - who they would be behind closed doors with his/their children.
The women will also get a chance to see how the MC interacts with younger children ... is he patient, engaged, helpful, etc.?
The MC might not have a lot of time to play with them given his other responsibilities but:
Does he carve out a space for them to play quietly?
Does he offer to teach an interested child a bit about cooking the way his grandfather taught him?
Does he include them in the after-work dinner get together and engage them in conversations - showing that he values their company and teaching them a measure of how to interact with others by the way he interacts with them?
The women in/near his harem - especially Allison, Misaki and even ELizabeth - are likely watching for clues about the man who might/will become both husband and father of their children.
Word will also get back to any founding family mothers of those children (as well as older siblings and eventually other mothers and fathers/founding family heads) of how the MC treats their relatives.
I think the amount of quiet relationship building that the MC can accomplish just being the good, caring guy that he is will be important for the ripples that carry out from his treatment of those young relatives.
In particular, his passion for cooking could be a great thing to share with one or two of the new side characters.
I still have a very fond memory of being a little guy and one of my grandmothers picked me up, put me on the kitchen counter and taught me how to make pancakes.
She's been gone for decades now but that memory is still almost as fresh as the day it was made.
The genuine engagement of a 'big person' with a 'little person' has lasting effects in RL and can have the same kind of impact in this story.
I think the introduction of younger siblings/relatives is a Very good addition and I'm looking forward to seeing how it happens in the next rev and the story into the future.
Cheers!!
