Ruling on loyalty to the Mushrik family
What should a son do who was raised by an ignorant family then he learned Islamic knowledge and informed his family of Haram (prohibited) and Halal (lawful) matters but his father refused claiming that they practice what they found their fathers following and that they do like what others do? Should this son do good to his parents brothers or not?
If one knows true Islam and Allah helps him accept it, one should not be loyal to people of Shirk (ascribing partners to Allah in worship) nor be endeared to them even if they are the closest relatives. Allah (may He be Exalted says: “You (O Muhammad صلى الله عليه وسلم) will not find any people who believe in Allâh and the Last Day, making friendship with those who oppose Allâh and His Messenger (Muhammad صلى الله عليه وسلم), even though they were their fathers or their sons or their brothers or their kindred (people).” (Al-Mujadilah: 22)
However, this son must call his family to Allah and urge them to do what is good and be patient in doing so. Perhaps Allah will guide them at his hands and he will take a reward equal to theirs.