All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
According to the view that the non-Muslims are ordered to abide by the rulings of Sharee’ah –as it is the correct opinion of the majority of the scholars of the principles of Fiqh –which is clarified in Fatwa 85569 it is not permissible to sell food to them in the daytime in Ramadan if it is known or predominantly thought that they will eat it during daytime, as mentioned in the Fataawa of Ar-Ramli from the Shaafi’i School of jurisprudence.
Therefore, it is not permissible for your brother to sell food to the non-Muslims if he knows that they will eat it during the daytime in Ramadan, because if one does so, then he is helping them in disobeying Allaah.
Allaah Knows best.