At what point did Paul become a child of God, born of God?

At what point did Paul become a child of God, born of God? John said that God gave the authority to be the children of God born of God to those who received Christ (John 1:12,13; 1st John 3:1). At what point did Paul become regenerate? Was it at his first encounter with the Lord on the way to Damascus (Acts 9:5,6)? Was it when he was baptized? Did it happen at a different time? Ananias called Paul a brother before Paul was baptized (Acts 9:17, 22:13). What is the meaning of this word, "brother?" Does it infer that Paul had met the qualifications to be called a child of God, born of God, that is written in John 1, or was Ananias using the word "brother" differently, perhaps in the Old Testament sense?