Is it permissible to pay Zakat al-Mal (obligatory charity on wealth) to a poor brother to cover the medical insurance costs for his mother and sister who are under his guardianship?

Commercial insurance is prohibited except in cases of necessity, such as mandatory insurance, or for need, such as health insurance when treatment costs are high. As for giving Zakat to one's mother or sister for insurance, there is a detailed explanation:

1. For the Mother: If you are wealthy and she is in need of insurance, it is obligatory for you and all her capable children to provide for her, and it is not permissible to give her from Zakat. However, if you are unable to provide for her, and you possess wealth upon which Zakat is due, then some scholars permit giving her from Zakat. 2. For the Sister: If you are her heir and she cannot pay for insurance, then her maintenance is obligatory upon you, and you give it to her as maintenance, unless you are unable, in which case you give her from Zakat. However, if you are not her heir, it is permissible to give her from Zakat if she is unable to pay for insurance.