John Gill

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 in the truth, and here send their Christian salutation to their aunt; very likely those sister's children lived at Ephesus, where John resided.