12:12 Who is the "John" referred to here whose surname was Mark?
12:12 Who is the "John" referred to here whose surname was Mark?
This is Mark who wrote the gospel that bears his name. Mark was Barnabas' cousin (CP Col 4:10). Sister's son (KJV) here means cousin. Mark accompanied Paul and Barnabas on their first apostolic mission (CP Ac 12:25-13:5).
But he left Paul and Barnabas in Perga under a cloud and returned to Jerusalem (CP 13:13 with 15:36-41). After that Mark accompanied Barnabas on his journeys for a time but later on we learn that he twice ministered the gospel with Paul while Paul was imprisoned in Rome (CP Col 4:10; Phm 24; 2Ti 4:11).
Peter called Mark his son - not his real son, but his son in the faith - the same way that Timothy and Titus were sons of Paul (CP 1Ti 1:2; Tit 1:4 with 1Pe 5:13); some Bible commentators think that Mark was referring to himself as the young man who fled naked when Jesus was arrested, but that is pure speculation and we cannot teach it (CP Mk 14:50-52).
It is interesting to note that even though Paul and Barnabas were involved in a very angry dispute with each other concerning Mark in Ac 15, they were reconciled again later on (CP Ac 15:39-40 with 1 Cor 9:6).