That would be a unique creature indeed!
Seems like everyone is talking past everyone else when all are in fact in general agreement.
Since salvation -- eternal life -- is God's GIFT to the one who truly repents and believes on Christ, salvation cannot be "lost". Neither can a child of God be "unborn".
By the same token the ones who are truly saved have been born again, and made new creatures in Christ. Therefore old things have passed away, and all things have become new. And that is why Christian baptism is so critical. It is a watershed experience to show the new convert that he is buried in the likeness of Christ's death, and raised again to walk in newness of life (by the power of the Spirit). Which means that those who are genuine children of God have turned their backs on sins and idols and turned wholeheartedly to God and Christ by faith.
For some, conversion is immediate and total (e.g. the apostle Paul). For others there may remain besetting sins. But simply because a Christian sins does not mean he loses his salvation. That is what Satan would have people to believe, but it is a lie of the devil.
Those who hold on to an evil or sinful lifestyle were never saved to begin with. So they need to repent and be converted.