The word(s) "brethren" appears 17 time(s) in 16 verse(s) in Quran in Muhammad Habib Shakir translation.

(11) Assert their relationship to their fathers; this is more equitable with Allah; but if you do not know their fathers, then they are your brethren in faith and your friends; and there is no blame on you concerning that in which you made a mistake, but (concerning) that which your hearts do purposely (blame may rest on you), and Allah is Forgiving, Merciful.

(12) Allah knows indeed those among you who hinder others and those who say to their brethren: Come to us; and they come not to the fight but a little,

(13) The believers are but brethren, therefore make peace between your brethren and be careful of (your duty to) Allah that mercy may be had on you.

(14) And Ad and Firon and Lut's brethren,

(15) And those who come after them say: Our Lord! forgive us and those of our brethren who had precedence of us in faith, and do not allow any spite to remain in our hearts towards those who believe, our Lord! surely Thou art Kind, Merciful.

(16) Have you not seen those who have become hypocrites? They say to those of their brethren who disbelieve from among the followers of the Book: If you are driven forth, we shall certainly go forth with you, and we will never obey any one concerning you, and if you are fought against, we will certainly help you, and Allah bears witness that they are most surely liars.