They were very likely Hellenistic Jews who lived in Palestine and fled the persecution of Saul of Tarsus, eventually journeying to Rome, and joining with the Jewish colony there.

7 Greet Andronicus and Junia, my countrymen and my fellow prisoners, who are of note among the apostles, who also were in Christ before me.
— Rom. 16:7

011418 Andronicus and Junia PP