Attribution of an illegitimate child and rulings that result from that
Question

                Thirty-two years ago an illegitimate child was born to a foreign kitaabi woman (i.e. Jewish or Christian woman). He is a young man of very good character and with a good heart. When he reached the age of 25, he started to look for his parents. He found his mother, and he found me, the father, a week ago. It has been proven by DNA testing that I am the father. I got married 31 years ago to a Muslim woman, and I have a daughter and two sons from her, and I have 4 grandchildren. Praise be to Allaah Who guided me, I came back to fear of Allaah and I am religiously-committed: I pray and give zakaah, and I did Hajj and ‘Umrah 3 years ago, my wife and I. I ask Allaah to guide me always and help me to repent. 

I hope that you can advise me: is he a mahram for my wife and daughter? Is he a brother to my children? Should I regard him as one of the family? I hope that you can explain everything that has to do with the matter.
Praise be to Allah.
    Firstly: 

    We ask Allaah to pardon us and you, and to help us to repent 
    properly and turn to Him, and to bless us with good and righteous offspring 
    by His grace and bounty. 

    Remember that repentance and guidance are the best things 
    that a person may be blessed with in this world; they are the greatest 
    blessings that Allaah can bestow upon us. So we must be grateful to Allaah 
    for them, and strive to renew them. The Prophet  (peace and blessings of 
    Allaah be upon him) used to pray to Allaah for forgiveness and repent to him 
    one hundred times every day, as was narrated by Muslim (2702). 

    Secondly: 

    With regard to the attribution of illegitimate children, the 
    fuqaha’ have discussed this issue in detail and they said that one of two 
    scenarios must apply to the woman with whom zina is committed: 

    1 – Either she is married, in which case any child who is 
    born to her is to be attributed to the husband and not to anyone else, even 
    if she is certain that he is the child of the one with whom she committed 
    zina, unless the husband disowns the child by means of li’aan, in which case 
    the child is not attributed to the husband, rather he is to be attributed to 
    his mother and not to the zaani (adulterer). 

    2 – Or she is not married. If an unmarried woman has a child, 
    the scholars differed as to whether the child should be attributed to his 
    father, the zaani, or to his mother. There are two opinions, which have been 
    discussed and the evidence for them quoted, in the answer to question no. 
    33591. See also the answers to questions no. 
    117, 
    2103 and 
    3625. There it 
    says that the correct view is that this attribution is not valid, so it is 
    not permissible to attribute the illegitimate child to the zaani, rather he 
    should be attributed to his mother, even if there is certainty that this 
    child was fathered by this zaani. 

    It says in Fataawa al-Lajnah al-Daa’imah (20/387): 

    The correct scholarly view is that the child is not to be 
    attributed to the man who had intercourse with the woman, unless intercourse 
    took place within the framework of a valid or invalid marriage or something 
    that may be taken as a marriage contract or concubinage or something that 
    may be taken as concubinage. In such cases, the child may be attributed to 
    the man who had intercourse with the woman, and they may inherit from one 
    another. But if it was a case of zina then the child cannot be attributed to 
    the zaani. Based on that, he cannot inherit from him. End quote. 

    It also says in Fataawa al-Lajnah al-Daa’imah 
    (22/34): 

    With regard to the illegitimate child, he is to be attributed 
    to his mother, and he comes under the same rulings as any other Muslim if 
    his mother is a Muslim. He is not to be blamed or put to shame for his 
    mother’s crime or the crime of the one who committed zina with her, because 
    Allaah says (interpretation of the meaning): 

    “And no bearer of burdens shall bear another’s burden”

    [Faatir 35:18]

    End quote. 

    Thirdly: 

    It is well known that attribution of lineage affects many 
    rulings such as rulings on breastfeeding, custody, guardianship, 
    maintenance, inheritance, qasaas, the hadd punishment for stealing, slander, 
    testimony etc. Because the more correct view is that the illegitimate child 
    cannot be attributed to the zaani, none of the rulings mentioned above can 
    be proven to apply to the father of the illegitimate child, rather many of 
    them apply to the mother. 

    But the illegitimate father (the zaani) is still affected by 
    the rulings forbidding marriage. According to the majority of scholars, the 
    rulings forbidding marriage still apply between the illegitimate child and 
    his father and his father’s relatives. 

    Ibn Qudaamah (may Allaah have mercy on him) said: 

    It is haraam for a man to marry his illegitimate daughter, or 
    his illegitimate sister, or his (illegitimate) son’s daughter, or his 
    daughter’s daughter, or his brother’s daughter, or his sister who is 
    illegitimate. This is the view of most of the fuqaha’. End quote. 

    Al-Mughni (7/485). 

    Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) 
    was asked about an illegitimate daughter –can she marry her father? 

    He replied:  
The view of the majority of scholars is 
    that it is not permissible to marry her. This is definitely the correct 
    view. End quote. 
    
    Majmoo’ al-Fataawa (32/134). 

    It says in al-Mawsoo’ah al-Fiqhiyyah (36/210): 

    It is haraam for a man to marry his illegitimate daughter, 
    because of the clear meaning of the verse (interpretation of the meaning): 

    “Forbidden to you (for marriage) are: your mothers, your 
    daughters…”

    [al-Nisa’ 4:23]

    because she is his daughter in a real sense and in linguistic 
    terms and she was created from his water (i.e. sperm), so the illegitimate 
    son is forbidden (in marriage) to his mother. 

    This is the view of the Hanafis and of the Maalikis and 
    Hanbalis. End quote. 

    Fourthly: 

    Based on the above, it is not permissible for this 
    illegitimate son of yours to marry your daughters, so they are his like 
    sisters. The same applies to your wife. 

    But that does not mean that he is a mahram for them in the 
    sense that they may be alone with him and take off their hijab in his 
    presence. Prohibition of marriage does not always mean that one is a mahram 
    in the sense that it is permissible to be alone with the person etc. This is 
    an additional ruling which applies only to the shar’i mahrams, so attention 
    must be paid to that. 

    Ibn Qudaamah (may Allaah have mercy on him) said: 

    Zina means that a person is forbidden in marriage, but it 
    does not make the person a mahram or make it permissible to look (at a 
    member of the opposite sex). End quote. 

    Al-Mughni (7/482). 

    This does not mean that you should not treat this young man 
    kindly and strive to bring him to Islam and make him a member of the family, 
    but he should not be attributed to his illegitimate father, and the issue of 
    the daughters of the family observing hijab in front of him should not be 
    taken lightly. We ask Allaah to bless you and guide you. 

    And Allaah knows best.