Is it permissible to count a portion of the inheritance that the questioner has not received from her brother as Zakat al-Mal (charity on wealth) to give to her sick sister who needs expensive medicine, given the father's refusal to buy it due to his low income?

It is permissible to give Zakat to a poor, sick sister if those responsible for her maintenance are unable to cover her treatment costs. She has a greater right to the Zakat, based on the Prophet Muhammad's (peace be upon him) saying: "Charity given to a relative is both charity and upholding ties of kinship." The money inherited from the mother became the questioner's property immediately upon her death, so he is permitted to dispose of it as he wishes, including giving it as Zakat to the sick sister, whether by authorizing the brother to pay it or by receiving it from him and then giving it to her. The Zakat payer's obligation is not fulfilled until the sister or her representative receives the money.