What is the ruling on shunning and cursing siblings based on the will of a father who was prone to much cursing and anger?

It is forbidden by consensus to curse a specific Muslim, and it is considered a grave sin. It is not permissible to obey one's father in shunning a brother, because there is no obedience to a creature in disobedience to the Creator. Permanent shunning of a brother is an act of disobedience, and the prohibition becomes even greater if the brother has not done anything to deserve being shunned. The father and brother should be advised gently and wisely: the father should be advised to avoid cursing, and the brother to honor his parents and avoid disobedience.