It takes much more than just believing that Jesus Christ is God, and he came to make it so we can become Children of God. To become a Child of God one has to receive the Holy Spirit. The Holy Spirit will teach, and give one the grace to keep God’s Commandments.
(Romans 8:1-4) “The reason, therefore, why those who are in Christ Jesus are not condemned, is that the law of the spirit of life in Christ Jesus has set you free from the law of sin and death. God has done what the Law, because of our unspiritual nature, was unable to do. God dealt with sin by sending his own Son in a body as physical as any sinful body, and in that body God condemned sin he did this in order the Law’s just demands might be satisfied in us, who behave not as our unspiritual nature but as the spirit dictates.”
When one is obeying God at all times then he or she becomes a Child of God.
(1 John 3:9-10) “No one who has been begotten by God sins; because God’s seed remains inside him, he cannot sin when he has been begotten by God. In this way we distinguish the children of God from the children of the devil: anybody not living a holy life and not loving his brother is no child of God’s”
Notice if one sins he or she is a child of the devil.