When a child is born it is not aware of any religion, culture, politics etc., it is just a human being eager to learn and explore as much as possible, it is a human being not bound to any cultural trait.
As the child grows this changes because the child learns from its family and surrounding area (where already there's a certain cultural trait) and is influenced by that and gets attached to it because it is what is implemented as normal to it. Then the school system does its job as well with forcing the study of certain cultural traits and behavior, and considering the years the child spends in school it leaves a deep mark in it.
The media does its share with the propaganda, and by looking and listening to certain things from a very young age the child tends to get attached to some of it at least.