When someone obeys the Gospel and trusts in the Lord Jesus as their saviour they are given the right to be called a child of God. How is this possible? Because of the victorious work, Jesus has completed at the cross.
Bible Scriptures: Darby Translation
John 1:11-12 “He came to his own, and his own received him not; but as many as received him, to them gave he the right to be children of God, to those that believe on his name”