See on Phm 1:23, Phm 1:24. Unnecessary difficulty is made over the fact that the term fellow-prisoner is applied to Epaphras in Phm 1:23, and not to Aristarchus; while here the case is reversed. It is not necessary to suppose that the two had changed places, or that the captivity was voluntary, if a literal captivity was meant. All the three terms fellow-prisoner, fellow-servant, fellow-worker - might be applied to both; and, as Dwight remarks, “Reasons unknown to us may easily have determined the use of one word or the other, independently of the question as to the particular time when they were in imprisonment.”
See on Phm 1:24.
Sister's son (ἀνεψιός)
Only here in the New Testament. Rev., correctly, cousin. The sense of nephew did not attach to the word until very late. Lightfoot remains that this incidental notice explains why Barnabas should have taken a more favorable view of Mark's defection than Paul, Act 15:37, Act 15:39.