We are all born free from all religious affiliations and only come to believe in such things after being introduced to it ― so, atheism is the default position. Although some children are not indoctrinated with a specific religion before the age of reason, there are many more who are.

Mom, Dad, I'm an Atheist - The Guide to Coming Out as a Non-Believer: (ed. Dangerous Little Books, 2012) - ISBN: 9781908675040