Some Christians baptise their children at a young age
Taught to pray, or attend 'Sunday School' to educate on their religion and be encouraged to live a Christian life.
Celebrate Christmas and Easter etc, to learn and understand their meanings
Catholic Schools help children to be brought up in this religion
Being brought up within a Christian family would mean a child is surrounded by those who are convinced of the existance of God - influenced by their views.
Learning about this religion can allow a child to decide for themselves if they want to follow that faith.
If a religion has been handed down through families, it might seem perfectly normal to also follow this belief.