What is the religious ruling on a brother who commits fornication, drinks alcohol and smokes shisha, watches pornographic films, and has insulted the Messenger of Allah, peace and blessings be upon him, and the Islamic religion, and Allah Almighty, twice? Is it permissible to ostracize him, knowing that he does not respect his mother's advice and mistreats his family, or is cutting off kinship ties considered a major sin?

Blasphemy against Allah, His Messenger, and the religion is major disbelief (kufr akbar). Therefore, you must advise your brother and teach him that he has departed from the religion of Muslims. Command him to renew his entry into Islam. If he responds, then inform him of the sanctity of major sins. If he does not respond, then abandon him and sever your relationship with him for the sake of Allah, for shunning people of transgression for Allah's sake is a form of connection with Him. Abandoning him is one of the great acts of obedience that draw one closer to Allah. Love, hatred, allegiance, and enmity for the sake of Allah are the foundations of faith. It is not permissible to show affection to one who opposes Allah and His Messenger. Refraining from greeting people of innovation, sins, and transgressors is a Sunnah.