so if we have kids in the society, the parents can voluntarily decide on contracts for services for the children, but those children do not get to voluntarily decide who their parents are or who get contracted to give the service, how is it then that the soceity could be called a voluntary society when it's only under certain conditions that humans can volunteer and we start our lives( and may end our lives) without being able to make those voluntary choices?
Because it's voluntary in the sense of no one forcing things on you as a rational adult.
Complaining that 'we didn't choose our parents' or that children have choices made for them by their parents because they're too young to know what they're doing is complaining about the unavoidable nature of reality itself and will get you nowhere.
You couldn't remedy these facts of nature by allowing kids to choose their parents or stupidly allowing those incapable of making decisions for themselves to do so.
so what philosophy and law goes into how the rational will treat the irrational?