Believers become children of God through Jesus (St. John 1:1-13), specifically:
12 But to those who did accept him he gave power to become children of God, to those who believed in his name 13 who were born not from human stock or human desire or human will but from God himself. (John 1:12-13)
But while we are granted inheritance along with Jesus, we remain not Divine and in a constant battle–St Paul explains it this way:
12 For it is not against human enemies that we have to struggle, but against the principalities and the ruling forces who are masters of the darkness in this world, the spirits of evil in the heavens. (Ephesians 6:12)
So our struggle is to maintain that Grace given to us through Christ–we are called to be sons (children) of God but that state of Fellowship/Grace/Birth remains tethered to Christ, His Word, His Divinity (St. John 15:1-1510). Regretfully, both Believers and non-Believers continue to wrestle against God’s Authority and Will… inevitably losing our inheritance!
5 For you can be quite certain that nobody who indulges in sexual immorality or impurity or greed – which is worshipping a false god – can inherit the kingdom of God. 6 Do not let anyone deceive you with empty arguments: it is such behaviour that draws down God’s retribution on those who rebel against him. 7 Make sure that you do not throw in your lot with them. 8 You were darkness once, but now you are light in the Lord; behave as children of light, (Ephesians 5:5-8)