Is it permissible for him to prepare food for a non-Muslim son during the day in Ramadaan
Question

                My husband was married to a foreign woman and has two sons from her. Since a young age they have been living with her and they follow her religion (Christianity). They come to see their father at the weekend but for four months the older son has been living with us. Naturally, he is not fasting in Ramadaan. My question is: sometimes his father prepares food for him (during the day). What is the ruling on that?.
Praise be to Allah.It is not permissible for a 
    Muslim to offer food during the day in Ramadaan unless that is to a person 
    who is excused for not fasting, such as one who is sick or travelling. But 
    if he has no excuse then it is not permissible to give him food, whether he 
    is a Muslim or a kaafir. 
As for giving food to a 
    Muslim who does not have an excuse, that is clear, because he is sinning by 
    not fasting, and it is not permissible to help him in his sin. 
As for the non-Muslim, he 
    is also sinning by not fasting in Ramadaan, because the minor issues of 
    sharee’ah are addressed to the kuffaar as is indicated by the evidence, and 
    this is the view of the majority of scholars. What is meant by the minor 
    issues of sharee’ah being addressed to the kuffaar is that the kuffaar are 
    obliged to pray and fast and do all duties, just as they are obliged to 
    observe the basic principle, which is to believe. So the kaafir will be 
    called to account on both counts, the basic principle and the minor issues, 
    and he will be punished for failing to observe the minor issues just as he 
    will be punished for failing to observe the basic principle, even though 
    observing the minor issue is not valid unless the basic principle is first 
    observed. 
So the kaafir who is able 
    to fast must fast, just as he must become Muslim. If he does not fast then 
    he is sinning by breaking the fast. Hence it is not permissible to help him 
    in this sin, rather he should be left to prepare his food for himself. 
Al-Nawawi (may Allaah have 
    mercy on him) said: The correct view which is followed by the scholars and 
    the majority is that the minor issues of sharee’ah are addressed to the 
    kuffaar, and silk is forbidden for them just as it is forbidden to the 
    Muslims. End quote from Sharh Muslim, 14/39. 
Al-Ramli (may Allaah have 
    mercy on him) narrated in Nihaayat al-Muhtaaj (5/274) that the 
    scholars ruled that it is haraam to sell food to kaafirs during the day in 
    Ramadaan. 
See also question no.
    49694. 
We ask Allaah to guide 
    these two young men and to set their affairs straight. 
And Allaah knows best.