There is a dangerous myth going around that “everyone” is a child of God.
If that is true then Jesus is a liar, as He referred to the pharisees (and all unbelievers) as children of Satan.
John 8:42-44, 47
42 Jesus told them, “If God were your Father, you would love me, because I have come to you from God. I am not here on my own, but he sent me. 43 Why can’t you understand what I am saying? It’s because you can’t even hear me! 44 For you are the children of your father the devil, and you love to do the evil things he does… 47 Anyone who belongs to God listens gladly to the words of God. But you don’t listen because you don’t belong to God.”
While it is true that God created humanity, not everyone is His child. It’s not until you call upon Him as your Lord and Savior and become born-again that you are born into His family. Only those who trust in Christ and believe He is who He claims to be are children of God.
23 Jesus continued, “You are from below; I am from above. You belong to this world; I do not. 24 That is why I said that you will die in your sins; for unless you believe that I Am who I claim to be, you will die in your sins.”
26 For you are all children of God through faith in Christ Jesus. 27 And all who have been united with Christ in baptism have put on Christ, like putting on new clothes. 28 There is no longer Jew or Gentile, slave or free, male and female. For you are all one in Christ Jesus.
12 But to all who believed him and accepted him, he gave the right to become children of God. 13 They are reborn—not with a physical birth resulting from human passion or plan, but a birth that comes from God.
If anyone tells you that we are all children of God, they are leading you astray and teaching contrary to the words of Christ. Being a child of God is a privilege given only to those who believe in Christ and are born again. Be wary of those who teach otherwise, they are liars like their father.