Godly parents cannot convert their children.  God alone can do this.  But they can lead them to Jesus, and bring them up in the fear of the Lord.  And when they have done this, they have done all they can do; for the Holy Spirit alone can change the heart.  They must be born again.  Christ has said it.  It is not a change of sentiment, nor an outward reformation of life; it is a new heart implanted by the Holy Spirit.