The keyword of 1John 1:3-7 is "fellowship", and John says every Christian has fellowship with three parties:
1. With the Apostles. v3 "so that you too may have fellowship with us"
2. With the Triune God. v3 "indeed our fellowship is with the Father, and with His Son Jesus Christ" and v6 "we have fellowship with Him"
3. With other believers. v7 "we have fellowship with one another"