What does « Brother » mean in the Quran?

And for you is half of what your wives leave if they have no child. But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt. And for the wives is one fourth if you leave no child. But if you leave a child, then for them is an eighth of what you leave, after any bequest you [may have] made or debt. And if a man or woman leaves neither ascendants nor descendants but has a brother or a sister, then for each one of them is a sixth. But if they are more than two, they share a third, after any bequest which was made or debt, as long as there is no detriment [caused]. [This is] an ordinance from Allah, and Allah is Knowing and Forbearing.

Prohibited to you [for marriage] are your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your [milk] mothers who nursed you, your sisters through nursing, your wives' mothers, and your step-daughters under your guardianship [born] of your wives unto whom you have gone in. But if you have not gone in unto them, there is no sin upon you. And [also prohibited are] the wives of your sons who are from your [own] loins, and that you take [in marriage] two sisters simultaneously, except for what has already occurred. Indeed, Allah is ever Forgiving and Merciful.

[Moses] said, "My Lord, indeed I do not possess except myself and my brother, so part us from the defiantly disobedient people."

And his soul permitted to him the murder of his brother, so he killed him and became among the losers.

Then Allah sent a crow searching in the ground to show him how to hide the disgrace of his brother. He said, "O woe to me! Have I failed to be like this crow and hide the body of my brother?" And he became of the regretful.

And [some] among their fathers and their descendants and their brothers - and We chose them and We guided them to a straight path.

And to the 'Aad [We sent] their brother Hud. He said, "O my people, worship Allah; you have no deity other than Him. Then will you not fear Him?"

And to the Thamud [We sent] their brother Salih. He said, "O my people, worship Allah; you have no deity other than Him. There has come to you clear evidence from your Lord. This is the she-camel of Allah [sent] to you as a sign. So leave her to eat within Allah 's land and do not touch her with harm, lest there seize you a painful punishment.

And to [the people of] Madyan [We sent] their brother Shu'ayb. He said, "O my people, worship Allah; you have no deity other than Him. There has come to you clear evidence from your Lord. So fulfill the measure and weight and do not deprive people of their due and cause not corruption upon the earth after its reformation. That is better for you, if you should be believers.

They said, "Postpone [the matter of] him and his brother and send among the cities gatherers

And We made an appointment with Moses for thirty nights and perfected them by [the addition of] ten; so the term of his Lord was completed as forty nights. And Moses said to his brother Aaron, "Take my place among my people, do right [by them], and do not follow the way of the corrupters."

And when Moses returned to his people, angry and grieved, he said, "How wretched is that by which you have replaced me after [my departure]. Were you impatient over the matter of your Lord?" And he threw down the tablets and seized his brother by [the hair of] his head, pulling him toward him. [Aaron] said, "O son of my mother, indeed the people oppressed me and were about to kill me, so let not the enemies rejoice over me and do not place me among the wrongdoing people."

[Moses] said, "My Lord, forgive me and my brother and admit us into Your mercy, for You are the most merciful of the merciful."

But their brothers - the devils increase them in error; then they do not stop short.

But if they repent, establish prayer, and give zakah, then they are your brothers in religion; and We detail the verses for a people who know.

O you who have believed, do not take your fathers or your brothers as allies if they have preferred disbelief over belief. And whoever does so among you - then it is those who are the wrongdoers.

Say, [O Muhammad], "If your fathers, your sons, your brothers, your wives, your relatives, wealth which you have obtained, commerce wherein you fear decline, and dwellings with which you are pleased are more beloved to you than Allah and His Messenger and jihad in His cause, then wait until Allah executes His command. And Allah does not guide the defiantly disobedient people."

And We inspired to Moses and his brother, "Settle your people in Egypt in houses and make your houses [facing the] qiblah and establish prayer and give good tidings to the believers."

And to 'Aad [We sent] their brother Hud. He said, "O my people, worship Allah; you have no deity other than Him. You are not but inventors [of falsehood].

And to Thamud [We sent] their brother Salih. He said, "O my people, worship Allah; you have no deity other than Him. He has produced you from the earth and settled you in it, so ask forgiveness of Him and then repent to Him. Indeed, my Lord is near and responsive."

And to Madyan [We sent] their brother Shu'ayb. He said, "O my people, worship Allah; you have no deity other than Him. And do not decrease from the measure and the scale. Indeed, I see you in prosperity, but indeed, I fear for you the punishment of an all-encompassing Day.

When they said, "Joseph and his brother are more beloved to our father than we, while we are a clan. Indeed, our father is in clear error.

And when he had furnished them with their supplies, he said, "Bring me a brother of yours from your father. Do not you see that I give full measure and that I am the best of accommodators?

So when they returned to their father, they said, "O our father, [further] measure has been denied to us, so send with us our brother [that] we will be given measure. And indeed, we will be his guardians."

He said, "Should I entrust you with him except [under coercion] as I entrusted you with his brother before? But Allah is the best guardian, and He is the most merciful of the merciful."