Im not Arc, but some of these are answerable.
1. No, not to my knowledge
2. 10(I believe, not sure if I miscounted or missed any in my save)
3. It doesnt affect the story too much, but having them there with you is sorta the game asking if you want to still have these side characters in the story, but they do havw some unique dialog later down the line. It doesnt hurt at all to have them so i would say do it
4. I can't answer 4. But I'm guessing there will be more kids