Brethren as usual means “fellow Christians” and seems to refer to a larger group than that mentioned in verse 19.

Good News Bible adds “here” after “brothers.” Most translations will need this word to make it clear that Paul is talking about people in the place from which he is writing.

Holy kiss means the kind of greeting appropriate for members of God’s people (verse 15). Kissing, of course, has various connotations in different cultures and at different times. If its use will have the wrong meaning here, a term for greeting with a more general meaning is preferable; for example, “Give a warm Christian greeting to each other” or “Greet each other in a warm Christian fashion.”

Quoted with permission from Ellingworth, Paul and Hatton, Howard A. A Handbook on Paul’s First Letter to the Corinthians, 2nd edition. (UBS Handbook Series). New York: UBS, 1985/1994. For this and other handbooks for translators see here .