Here are some of the ways the families are significant, I'm not sure how far you are in the story yet tho. I read this book last year, so I can't remember which parts these are from
1) The way they have 2 children to a family, one male and one female
2) Raising children were rules in the community
3) The parents aren't the real birth givers of the children, you had to apply for kids
4) Very controlled family with special practices
Hope this helps! (I believe it's all before chapter 10)
No, I don't think it is a rhetorical device
