Her brother is very audacious in committing sin – what should she do with him?
Question

                I have a brother who is younger than me, 20 years old. I know that he commits all the sins that Allaah has forbidden, and my father and mother are righteous but they cannot set him straight. I fear for him but every time I try to speak to him he reacts by telling me than he has no aim in life and he wants to die. He always says why should I set myself straight and for whom? What can I do for my only brother?.
Praise be to Allah.
    I ask Allaah to bless your brother with guidance and 
    righteousness, and to bring him back to the straight path, and to help you 
    to call him and guide him to what is good and to make that count in the 
    balance of your good deeds. 

    You should note – may Allaah bless you – that there are a 
    number of ways in which you can call your brother and guide him. These 
    include the following: 

    Firstly: Pray sincerely for your brother to be guided and set 
    aright, and have certain faith that Allaah will respond. Keep on praying for 
    that, and know that Allaah will never let down the one who puts his hope in 
    Him or refuse to answer the one who prays to Him with sincerity. 

    Secondly: Try to advise him sincerely, seeking to convince 
    him rationally. Encourage him by telling him of the honour and great reward 
    that Allaah has prepared, and warn him by telling him of the punishment and 
    humiliation and severe torment that Allaah has prepared for the sinners. 
    Tell him about the true nature of this life, and that Allaah has only 
    created this universe – with its earth and heaven, seas and rivers, 
    mountains and plains, lowlands and deserts, for you, O man. How can you, O 
    weak creature, compare to these mighty creations which Allaah has subjugated 
    for you, to make your life easier, as Allaah says (interpretation of the 
    meaning): 

    “He it is Who created for you all that is on earth”

    [al-Baqarah 2:29] 

    “He it is Who has made the earth subservient to you (i.e. 
    easy for you to walk, to live and to do agriculture on it); so walk in the 
    path thereof and eat of His provision. And to Him will be the Resurrection”

    [al-Mulk 67:15] 

    “See you not (O men) that Allaah has subjected for you 
    whatsoever is in the heavens and whatsoever is in the earth, and has 
    completed and perfected His Graces upon you, (both) apparent (i.e. Islamic 
    Monotheism, and the lawful pleasures of this world, including health, good 
    looks) and hidden [i.e. one’s faith in Allaah (of Islamic Monotheism), 
    knowledge, wisdom, guidance for doing righteous deeds, and also the 
    pleasures and delights of the Hereafter in Paradise]?”

    [Luqmaan 31:20]
Indeed He has preferred 
    you above all these earthly creations, as He says (interpretation of the 
    meaning): 

    “And indeed We have honoured the Children of Adam, and We 
    have carried them on land and sea, and have provided them with At‑Tayyibaat 
    (lawful good things), and have preferred them above many of those whom We 
    have created with a marked preferment”

    [al-Isra’ 17:70]

    If you know this, O weak creature, and that Allaah has 
    created all these great creations and subjugated them for your comfort in 
    this life, then hasten to ask the logical question which occurs to every 
    wise person: Why did Allaah create me then? Your Lord and Creator has 
    clearly answered this question, as He says (interpretation of the meaning): 

    “And I (Allaah) created not the jinn and mankind except 
    that they should worship Me (Alone)”

    [al-Dhaariyaat 51:56]

    So the purpose for which you have been created, O man, is 
    this: To submit yourself truly and sincerely to Allaah, the One, the Only. 
    This is the answer to your question: for whom should I set myself straight? 
    You should set yourself straight for Allaah Who has created you and formed 
    you, Who has given you life, strength and health, and all the blessings that 
    you enjoy. They all come from Him alone, and if He so willed He could take 
    them all away from you in the blink of an eye. Does He not deserve that you 
    should your gratitude for these innumerable blessings by doing what He 
    commands and avoiding what He has forbidden, which is the essence of the 
    worship for which you were created. With regard to your saying why should I 
    set myself straight, Allaah has stated the reason why He created death and 
    life in this world. It is so that you may know the greater reality which, 
    once a man knows it, he cannot have any peace of mind until he attains the 
    pleasure of Allaah and meets Him in Paradise. Allaah says (interpretation of 
    the meaning): 

    “Who has created death and life that He may test you which 
    of you is best in deed. And He is the All‑Mighty, the Oft‑Forgiving”

    [al-Mulk 67:2]

    So you should understand this and understand that your 
    Creator is testing you now, in this world, to see what you will do and to 
    recompense you accordingly on the Day when you meet Him – if it is good then 
    you will be rewarded and if it is bad then you will be punished – and you 
    should understand that after death man will never be left neglected, rather 
    he will be recompensed according to his deeds as Allaah says (interpretation 
    of the meaning): 

    “Does man think that he will be left neglected (without 
    being punished or rewarded for the obligatory duties enjoined by his Lord 
    Allaah on him)?”

    [al-Qiyaamah 75:36],   
Based on this, you will 
    notice that Allaah often describes in His Book what He has prepared for His 
    slaves who do good in this world, for in the Hereafter they will have with 
    Him Paradise that is as wide as the heavens and the earth, in which there is 
    what no eye has seen, no ear has heard and it has not entered the heart of 
    man. And He also often describes what He has prepared for those who do evil 
    and neglect His rights over them; it is blazing Fire in which they will 
    neither live nor die, in which He has prepared all kinds of humiliation and 
    torment which would cause a child’s hair to turn white if he heard of them, 
    let alone saw them with his own eyes. We ask Allaah to keep us and you safe 
    from it. 

    After knowing all this, is it befitting for you to dare to go 
    against His commands or to live for any purpose other than that for which 
    you have been created? By Allaah the poet spoke the truth when he said: 

    If when we die we are abandoned, then death would be the end 
    of every living thing

    But when we die we will be resurrected and asked after that 
    about everything. 

    Undoubtedly the anxiety and worry that you are feeling make 
    you wish for death; that is because you have lost the sense of this noble, 
    divinely-ordained goal. The greatest and most enjoyable thing in this 
    universe is to be a true slave of Allaah. So beware of turning away from 
    your Lord and becoming far away from Him, for you will return to Him even if 
    you live a very long life, as Allaah says (interpretation of the meaning): 

    “O man! Verily, you are returning towards your Lord  with 
    your deeds and actions (good or bad), a sure returning, and you will meet 
    (the results of your deeds which you did).”

    [al-Inshiqaaq 84:6]
Beware lest you meet Him 
    having turned away from Him, and the following words apply to you 
    (interpretation of the meaning): 

    “But whosoever turns away from My Reminder (i.e. neither 
    believes in this Qur’aan nor acts on its teachings) verily, for him is a 
    life of hardship, and We shall raise him up blind on the Day of 
    Resurrection.

    125. He will say: ‘O my Lord! Why have you raised me up 
    blind, while I had sight (before).’

    126. (Allaah) will say: ‘Like this: Our Ayaat (proofs, 
    evidences, verses, lessons, signs, revelations, etc.) came unto you, but you 
    disregarded them (i.e. you left them, did not think deeply in them, and you 
    turned away from them), and so this Day, you will be neglected (in the 
    Hell‑fire, away from Allaah’s Mercy).’

    127. And thus do We requite him who transgresses beyond 
    bounds [i.e. commits the great sins and disobeys his Lord (Allaah) and 
    believes not in His Messengers, and His revealed Books, like this Qur’aan], 
    and believes not in the Ayaat (proofs, evidences, verses, lessons, signs, 
    revelations, etc.) of his Lord; and the torment of the Hereafter is far more 
    severe and more lasting”

    [Ta-Ha 20:124-127]

    So hasten to repent sincerely, and you will find a Lord Who 
    is generous and rejoices over His slave when he repents, and is pleased with 
    him when he repents. Indeed He bestows such love and mercy upon him that has 
    never crossed anyone’s mind. So what are you waiting for? Allaah says 
    (interpretation of the meaning): 

    “So flee to Allaah (from His Torment to His Mercy 
    – Islamic Monotheism). Verily, I 
    (Muhammad) am a plain warner to you from Him”

    [al-Dhaariyaat 51:50]

    Once you have understood this, then note – may Allaah help 
    you to do that which pleases Him – that this great blessing, salvation from 
    that painful torment and success in this great test can only be attained by 
    means of hard work and difficulty which requires patience, perseverance and 
    longsuffering. But it is a hardship that will quickly pass and suffering 
    that will soon end, to be followed by eternal bliss and everlasting 
    pleasure. What is a little hardship and pain when compared with eternal 
    delight and everlasting joy. 

    We ask Allaah to bless us all with His bounty and His 
    Paradise… 

    In conclusion, I would like to leave you with these great 
    verses from the Book of Allaah, which He revealed to His slave Muhammad  
    (peace and blessings of Allaah be upon him) to be a healing for the hearts 
    of the believers and a remedy for their ills, so read them and ponder their 
    meaning, so that Allaah may make them a balm and a healing for the anxiety 
    and distress that you are suffering.  

    Our Lord said (interpretation of the meaning): 

    “Verily, those who say: ‘Our Lord is Allaah (Alone),’ and 
    then they stand firm, on them the angels will descend (at the time of their 
    death) (saying): ‘Fear not, nor grieve! But receive the glad tidings of 
    Paradise which you have been promised!

    31. ‘We have been your friends in the life of this world 
    and are (so) in the Hereafter. Therein you shall have (all) that your 
    inner‑selves desire, and therein you shall have (all) for which you ask.

    32. ‘An entertainment from (Allaah), the Oft‑Forgiving, 
    Most Merciful’”

    [Fussilat 41:30-32]

    “Verily, those who say: ‘Our Lord is (only) Allaah,’ and 
    thereafter stand firm (on the Islamic Faith of Monotheism), on them shall be 
    no fear, nor shall they grieve.

    14. Such shall be the dwellers of Paradise, abiding 
    therein (forever)-a 
    reward for what they used to do”

    [al-Ahqaaf 46:13-14]

    “O you who believe! Fear Allaah and keep your duty to Him. 
    And let every person look to what he has sent forth for the morrow, and fear 
    Allaah. Verily, Allaah is All‑Aware of what you do.

    19. And be not like those who forgot Allaah (i.e. became 
    disobedient to Allaah), and He caused them to forget their ownselves (let 
    them to forget to do righteous deeds). Those are the Faasiqoon (rebellious, 
    disobedient to Allaah).

    20. Not equal are the dwellers of the Fire and the 
    dwellers of the Paradise. It is the dwellers of Paradise that will be 
    successful”

    [al-Hashr 59:18-20]

    And there are many other verses which explain this great 
    truth clearly. So you must turn to the Book of Allaah, in which you will 
    find all that is good, and keep away from everything that is bad and evil. 

    I ask Allaah to open your heart to goodness and to make you 
    steadfast in adhering to it until you meet Him; and to keep evil away from 
    you, for He is All-Hearing, Ever-Near. And Allaah knows best.