What does Romans 16:21 mean?
Paul has previously sent his greetings to specific people in Rome. Now he sends greetings from specific people with him in Corinth.He first sends greetings from his fellow worker Timothy. Timothy worked as one of Paul's closest partners in ministry, serving alongside and supporting the apostle for many years, beginning with the second missionary journey (Acts 16:2–3). He was present for the writing of many of Paul's letters, including 2 Corinthians, 1 Thessalonians, 2 Thessalonians, Philippians, Colossians, and Philemon. Timothy was with Paul during his time in prison in Rome and afterwards.
Paul wrote two pivotal letters of the New Testament to Timothy, as well: 1 and 2 Timothy. Among other things, these explain how Timothy was to serve the church in Ephesus as a young pastor.
Paul also sends greetings from three other men with him at the time, identified as kinsmen—Jews along with Paul. It's unclear who Lucius was, but Jason may very well have been the man who took so much abuse for receiving Paul when he was in Thessalonica (Acts 17:5–9). Sosipater may be Sopater the Berean, mentioned in Acts 20:4, who went with Paul during his third missionary journey. It's possible that all three men served as representatives of the churches sending money to the poor Jewish Christians in Jerusalem.