Allaah has obliged sons to honour their parents and He has forbidden them to disobey them. We have discussed some of their (parents’) rights in the answer to question no. 5053.
What you have said about your brother’s treatment of your parents is an evil action and is a major sin. You have to advise him and remind him of what Allaah has enjoined upon him towards his parents and relatives.
It is not permissible for you to accuse others of practicing witchcraft against your brother. The Prophet (peace and blessings of Allaah be upon him) warned us against suspicion, and told us that it is the falsest of speech. It was narrated from Abu Hurayrah that the Prophet (peace and blessings of Allaah be upon him) said: “Beware of suspicion, because suspicion is the falsest of speech; do not spy on one another, do not pry into others’ affairs, do not hate one another; be brothers.” Narrated by al-Bukhaari, 4849; Muslim, 2563.
So you have to look for the reasons why your brother is doing this to you. There may be causes that you can put a stop to and help him to overcome.
If there is no apparent reason, there is nothing wrong with asking someone whose religious commitment and knowledge you trust to recite ruqyah for him and find out what is going on. If he finds out that he has been bewitched, then you have to treat him with remedies that will remove that sihr (magic), remedies that are proven in the Qur’aan and Sunnah.
Whatever the case, such a situation requires deliberation and wisdom in your dealing with him. Whether he is disobeying his Lord by treating his parents badly or he has been bewitched, he is sick, and the sick person needs to be treated kindly in order to find the most suitable remedy for his condition.
We ask Allaah to set the affairs of all the Muslims straight.
And Allaah is the Source of strength.