Once again, books 1-6 have all been about this supposed "Guardian" class of people that are divided into two sections: gold and silver, i.e. true guardians and auxiliaries. Well among other things, book six talks about marriage and children among the guardians. Plato/Socrates places love of the state above ALL else (seemingly on par with love of the gods, which I think might be a part of why he was put to death). So, in light of that view book six makes sense, though I think he overlooks some important parts of the human nature. First, a bit about what he says about marriage and children in this perfect state:
Basically, women will be given the same rights and responsibilities as men (which, in that day was very forward-thinking). However, when it comes to marriage and children all the guardians will share all the women and children. At a large marriage festival, everyone will gather and the lower classes will be deceived into thinking their marriages were drawn by luck/lot but in reality it's just to keep the lower classes in line and maintain the purity of the gene pool of the guardian class. So, all the guardians will be mated with other guardians and their children will be immediately taken from them and sent to guardian nursery/training schools to be cared for by specially chosen nursemaids. The mothers will be only brought in to supply milk and they will be carefully matched so they don't ever nurse their own child(ren). All the children of a certain age, will call each other 'brother/sister' and call all the people of their parent's generation 'father/mother,' and the previous generation 'grandfather/grandmother.' Here's the worst part: all the children of the guardian-class couples will be evaluated shortly after birth and if they are found defective they're thrown out like trash and killed, basically, state-sanctioned infanticide.
While the concept of a society-family would be nice (there have been other cultures that do something similar, Korean culture is much more familial than western culture) I don't think this kind of concept will really work. There's an interesting example in the Bible of state-sanctioned infanticide... it gave birth to Moses, one of Israel's greatest heroes. I think that Plato/Socrates is greatly underestimating the power of a mother's connection to her offspring; mothers really do have deep connections with their children and wouldn't be able to give them up so easily. I've said this before, and I'll say it again... I would never want to live in this type of society. No matter how good a state is it cannot replace family. The Nazis tried this kind of eugenics and failed (more or less). Only the people in charge want to perpetuate this kind of system. I'm glad that Plato didn't write our constitution because if our state wanted to mandate arranged state-sanctioned marriage and infanticide I'd refuse to have any part in it.