I've come in contact with quite a few former Christians who are now atheists. In all instances, the atheists were very conservative evangelical/fundamentalists. The charge is often leveled against them that they were never true Christians in the first place. Part of what's included in that charge is something along the lines of the atheist had more faith in the factual knowledge of the Bible, or the faith was too dependent on the factual knowledge of the Bible, rather than God Himself. Because the faith was so rigid, and not properly dependent upon knowing God, the atheist lost his faith for that reason.
These atheists have family members who are still the conservative evangelical/fundamentalists that the atheists once were. So if the atheists were never Christians because they never knew God, and because the faith was too tied up in a rigid view of the Bible, doesn't that mean that the family members who are currently Christians aren't Christians as well?