Epaphras.

Colossians 1:7
You learned it from Epaphras, our beloved fellow servant, who is a faithful minister of Christ on our behalf,

Colossians 4:12
Epaphras, who is one of you and a servant of Christ Jesus, sends you greetings. He is always wrestling in prayer for you, so that you may stand mature and fully assured in the full will of God.

my fellow-prisoner.

Romans 16:7
Greet Andronicus and Junias, my fellow countrymen and fellow prisoners. They are distinguished among the apostles, and they were in Christ before I was.

Colossians 4:10
My fellow prisoner Aristarchus sends you greetings, as does Mark the cousin of Barnabas. You have already received instructions about him: If he comes to you, welcome him.