The word(s) "brethren" appears 21 time(s) in 21 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) (Their bearings) on this life and the Hereafter. They ask thee concerning orphans. Say: "The best thing to do is what is for their good; if ye mix their affairs with yours, they are your brethren; but Allah knows the man who means mischief from the man who means good. And if Allah had wished, He could have put you into difficulties: He is indeed Exalted in Power, Wise."

(2) And hold fast, all together, by the rope which Allah (stretches out for you), and be not divided among yourselves; and remember with gratitude Allah's favour on you; for ye were enemies and He joined your hearts in love, so that by His Grace, ye became brethren; and ye were on the brink of the pit of Fire, and He saved you from it. Thus doth Allah make His Signs clear to you: That ye may be guided.

(3) O ye who believe! Be not like the Unbelievers, who say of their brethren, when they are travelling through the Earth or engaged in fighting: "If they had stayed with us, they would not have died, or been slain." This that Allah may make it a cause of sighs and regrets in their hearts. It is Allah that gives Life and Death, and Allah sees well all that ye do.

(4) (They are) the ones that say, (of their brethren slain), while they themselves sit (at ease): "If only they had listened to us they would not have been slain." Say: "Avert death from your own selves, if ye speak the truth."

(5) (To them) and to their fathers, and progeny and brethren: We chose them, and we guided them to a straight way.

(6) To the 'Ad people, (We sent) Hud, one of their (own) brethren: He said: O my people! worship Allah! ye have no other god but Him will ye not fear (Allah)?"

(7) To the Thamud people (We sent) Salih, one of their own brethren: He said: "O my people! worship Allah: ye have no other god but Him. Now hath come unto you a clear (Sign) from your Lord! This she-camel of Allah is a Sign unto you: So leave her to graze in Allah's earth, and let her come to no harm, or ye shall be seized with a grievous punishment.

(8) To the Madyan people We sent Shu'aib, one of their own brethren: he said: "O my people! worship Allah; Ye have no other god but Him. Now hath come unto you a clear (Sign) from your Lord! Give just measure and weight, nor withhold from the people the things that are their due; and do no mischief on the earth after it has been set in order: that will be best for you, if ye have Faith.

(9) But their brethren (the evil ones) plunge them deeper into error, and never relax (their efforts).

(10) But (even so), if they repent, establish regular prayers, and practise regular charity,- they are your brethren in Faith: (thus) do We explain the Signs in detail, for those who understand.