All 7 Uses of

brethren
in
The Iliad by Homer (translated by: Lang, Leaf, & Myers)

And now behold I all the other glancing-eyed Achaians, whom well I could discern and tell their names; but two captains of the host can I not see, even Kastor tamer of horses and Polydeukes the skilful boxer, mine own brethren, whom the same mother bare.†
Book 3

Now when Hector came to the Skaian gates and to the oak tree, there came running round about him the Trojans' wives and daughters, enquiring of sons and brethren and friends and husbands.†
Book 6 *

Yet doth the anguish of the Trojans hereafter not so much trouble me, neither Hekabe's own, neither king Priam's, neither my brethren's, the many and brave that shall fall in the dust before their foemen, as doth thine anguish in the day when some mail-clad Achaian shall lead thee weeping and rob thee of the light of freedom.†
Book 6

Then Zeus that gathereth the clouds spake to Apollo: "Prithee, dear Phoebus, go take Sarpedon out of range of darts, and cleanse the black blood from him, and thereafter bear him far away, and bathe him in the streams of the river, and anoint him with ambrosia, and clothe him in garments that wax not old, and send him to be wafted by fleet convoy, by the twin brethren Sleep and Death, that quickly will set him in the rich land of wide Lykia.†
Book 16

He went down the hills of Ida to the dread battle din, and straight way bore goodly Sarpedon out of the darts, and carried him far away and bathed him in the streams of the river, and anointed him with ambrosia, and clad him in garments that wax not old, and sent him to be wafted by fleet convoy, the twin brethren Sleep and Death, that swiftly set him down in the rich land of wide Lykia.†
Book 16

Then thirdly Helen led their sore lament: "Hector, of all my brethren of Troy far dearest to my heart!†
Book 24

First quenched they with bright wine all the burning, so far as the fire's strength went, and then his brethren and comrades gathered his white bones lamenting, and big tears flowed down their cheeks.†
Book 24

Definition:

brothers or members of the same community or group -- especially male members of a religious order