John the Apostle
2 John 1:13BSB·traditional attribution

The children of your elect sister send you greetings.

Matthew Henry Presbyterian @wholebiblehenry

The apostle concludes this letter, 1. With an adjournment of many things to personal conference: Having many things to write unto you I would not write with paper and ink; but I trust to come unto you, and speak face to face, that our joy may be full. Here it is supposed that some things are better spoken than written.

Commenting on 2 John 1:12-13

John Gill Reformed Baptist @doctorgill

The children of thy elect sister greet thee. Amen. Not the members of a sister church, as some think; but the children of one who was the sister of this lady, according to the flesh; and who, as she was either a very famous and excellent person, or rather one chosen of God likewise unto eternal life and salvation; and whose children also were walking...

Albert Barnes Presbyterian @notesbybarnes

Verse 13. The children of thy elect sister greet thee. Of this "elect sister" nothing more is known. It would seem probable, from the fact that she is not mentioned as sending her salutations, that she was either dead, or that she was absent. John mentions her, however, as a Christian--as one of the elect or chosen of God. REMARKS ON THIS EPISTLE.