As a baby is growing into a toddler and is starting to learn how to walk and talk, it begins to imitate it's parents actions. If the parents are a good influence and are teaching the child good manners and proper English then that child is going to imitate this. But, likewise if the child is being taught things like bad language and shown bad things to do then the child will mimic these actions. So it really depends on the parents to decide what way they raise their children.
From experience of working with children, I find that most children would have the personality/characteristics of at least one of it's parents. I often notice that girls tend to be more like their mothers while boys tend to be more like their fathers. Usually when there is a little boy with a quiet father then that boy will be quite whereas when the boy has a loud father he will tend to be loud. And it's pretty much the same with girls and their mothers. A quiet mother has a quiet child and a loud mother has a loud child. This is due to the fact that they become so used to the ways of their parents that they don't know any different. Even when they are in school they don't change because it's what their parents told them is right.
So to summarise, I firmly believe that when we are born we are neutral and we're completely oblivious to the world around us. I believe that our personalities and habits are picked up by mimicking the actions of those around us especially the people who brought us into this world, our parents.
MG