Consider the following situation.
There are parents, who leave the Islam and they will be atheists, or non-Muslims. Which is a serious crime, but it is possible.
They have children, and these children are grown up in other religion (or to be an atheist), and they never hear from the Islam.
Will these children be considered Muslims (because their parents were once Muslims), or they will have non-Muslim status?
P.s. It is a hypothetical question, actually I never heard any similar case. I am just curious, what happens in such a case.