Custody of a Muslim’s children from a kaafir wife if he dies
Question

                If the muslim man dies, to whom does the custody of the children goto if the wife is a christian, and the only muslim relatives of the man are far away?.
Praise be to Allah.Custody of the children 
    should not be given to a kaafir. This is the view of Maalik, al-Shaafa’i and 
    Ahmad. (al-Mughni, 11/412). If the Muslim relatives of the man are 
    far away, then the children should be sent to them. If that is not possible 
    then the children should be given to a Muslim family to take care of them 
    and have custody of them. 

    The conditions of custody include the following: 

    Being Muslim, for custody cannot be given to a kaafir. 

    Being of sound mind, for custody cannot be given to one who 
    is insane or mentally deficient. 

    Being an adult, for custody cannot be given to a minor. 

    Being able to bring them up properly, for custody cannot be 
    given to one who will be negligent. 

    Ibn al-Qayyim said: 

    No custody can be given to a kaafir over a Muslim for two 
    reasons: 

    1 – The one who is given custody of a child will be keen to 
    bring him up in his religion and to teach him about it, and after he grows 
    up it will be difficult for him to change. He may change him from the 
    natural disposition of man with which Allaah has created His slaves, and 
    after that he may never come back to it, as the Prophet  (peace and 
    blessings of Allaah be upon him) said: “Every child is born in a state of 
    fitrah (natural disposition of man), then his parents make him into a Jew or 
    a Christian or a Magian.” There is no guarantee that the one who has custody 
    will not turn a Muslim child into a Jew or Christian. 

    If it is said that the hadeeth only applies to the parents, 
    we should say that the hadeeth refers to the usual situation, which is that 
    a child usually grows up with his parents, but if one or both are lost, then 
    the child’s guardian among his relatives takes their place. 

    2 – Allaah has severed the ties of closeness between Muslims 
    and kaafirs, and has made the Muslims the close friends of one another, and 
    the kaafirs the close friends of one another. Custody is one of the 
    strongest reasons for creating close bonds, which Allaah has severed between 
    the two groups. 

    Zaad al-Ma’aad, 5/459. 
And Allaah knows best.