What does it mean that Paul calls Timothy his brother?

Paul refers to Timothy as our brother. Terms like brother and sister were common in the New Testament church, and indicated that there was a very close—indeed a familial—relationship between Christians. However, a careful examination of Paul’s use of the word brother shows that he often uses it to distinguish a certain group of people from the wider body of Christians; the people so designated are Paul’s coworkers (see 1 Corinthians 16:19–20; 2 Corinthians 8:18, 2 Corinthians 8:23; 2 Corinthians 9:3, 2 Corinthians 9:5; Ephesians 6:23–24; Philippians 1:14; Philippians 4:21–22; Colossians 4:15).^1,2 Thus, by calling Timothy our brother, Paul affirms his role as a minister of the gospel. This is significant, considering that Timothy was young and had joined Paul’s ministry team only a short while earlier—perhaps only a few months earlier (Acts 16:1–3). The affirmation would have encouraged the Thessalonian Christians to pay careful attention to what Timothy had said to them when he was in Thessalonica.