What is the ruling on assisting a brother who is unemployed and involved in an illicit relationship, while the mother insists on the necessity of spending on him?

The maintenance of a woman is incumbent upon her brother under three conditions: that the brother be poor, having neither wealth nor earnings; that the one providing maintenance possesses more than his own needs; and that the provider be an heir. If any of these conditions are not met, then maintenance is not obligatory. If the brother spends the maintenance on unlawful things, such as fornication, then maintenance must be withheld from him.