An excerpt from "Got Questions.org" entitled, "What Does it mean that we are children of God (1 John 3:2)?" states: "Being children of God means we have been born into God’s family. We become God’s children through faith in Jesus Christ, which results in spiritual rebirth: “But to all who believed him and accepted him, he gave the right to become children of God. They are reborn—not with a physical birth resulting from human passion or plan, but a birth that comes from God” (John 1:12–13, NLT; see also Galatians 3:26; 1 John 5:1)." This article may be viewed at: What Does it mean that we are children of God/gotquestions.org
Reference: Romans 9:26