Is her brother still a believer in God, given his insistence on marrying a divorced woman with two children despite his family's opposition and his changed behavior, and can it be determined whether he has been subjected to sorcery?

It is advised not to prevent marriage between two people who love each other, unless there is a legitimate religious impediment, based on the Prophet’s (peace be upon him) saying: "Nothing like marriage is seen for two who love each other." If there is a legitimate religious impediment, the young man must obey his father and practice chastity, striving against his own desires in this regard, for "whoever seeks to be chaste, Allah makes him chaste." As for magic, a person protects themselves by reciting the Quran and the Prophetic supplications (adhkar), especially the Mu'awwidhat (Surahs Al-Falaq and An-Nas) in the morning and evening, before sleeping, and after prayers, for the remembrance of Allah is a fortress against Satan. It is also advised to frequently supplicate for the brother's guidance and a good outcome.