John Chrysostom

"He spake unto them," it says, "in the Hebrew tongue, saying, Men, brethren, and fathers, hear ye my defence which I make now unto you." Mark his address, at once so free from all flattery, and so expressive of meekness. For he says not, "Masters," nor "Lords," but, "Brethren," just the word they most liked: "I am no alien from you," he says, nor "against you." "Men," he says, "brethren, and fathers:" this, a term of honor, that of kindred. …

Homily on Acts 47 ↗

Theophylact of Ohrid

The expression "fathers" is a sign of respect, and the expression "brethren" is an indication of kinship. Notice, his speech is both free from flattery and full of gentleness. He did not say "lords," but "brothers," which was especially pleasing to the people. I am not a stranger to you, he says, nor am I against you.

Commentary on Acts ↗

Cassiodorus

"Men, brethren, hear ye the account which I now give unto you," etc. Paul, being inclined to simplicity of heart, told the people, in order, how he had been chosen by the Lord when he was a persecutor of the church; he did not even fail to mention, with a broken heart, his crime relating to Stephen's blood; but he said that he had heard from the Lord, whom he could not oppose, that he would be sent to preach to the Gentiles. …

Complexiones on the Acts of the Apostles ↗