What should I do about my brother who frequently curses God to provoke me, despite his observance of prayer, and is it obligatory to visit him nonetheless so that I am not considered one who severs ties of kinship?

Islamic law commands maintaining kinship ties and forbids severing them, and it does not prohibit maintaining ties with a wicked relative or a disbeliever. However, it is not permissible to sit with a brother who commits acts and utters words of disbelief, for Allah Almighty says: "And He has already sent down to you in the Book that when you hear the verses of Allah disbelieved in and ridiculed, then do not sit with them until they enter into another conversation. Indeed, you would then be like them." Al-Qurtubi interpreted this as the obligation to avoid those who commit sins if a reprehensible act becomes apparent from them, and whoever sits in a gathering of sin and does not object must leave them. Islamic law did not specify a particular method for maintaining kinship ties; rather, it is left to custom, so it is achieved through visits, calls, and correspondence. Among the greatest forms of maintaining ties with a brother is enjoining what is right, forbidding what is wrong, and inviting him to repentance. If he does not repent, then there is no blame in boycotting and abandoning him; rather, it may be obligatory if that is a means to reforming him.