Chapter 34 — Part IV: Prayer — The Lord's Prayer: Introduction and Our Father Who Art in Heaven
Section 27. "Our" — When we invoke the Father and when each one of us calls Him our Father, we are to understand thereby that from the privilege and gift of divine adoption it necessarily follows that all the faithful are brethren and should love each other as such: You are all brethren for one is your Father who is in heaven." This is why the Apostles in their Epistles address all the faithful as brethren.