Is it permissible to give charity to a widowed relative who has four sons, two of whom regularly provide for her, a third who currently does not provide, and a fourth who provides intermittently, knowing that she is ill and needs medicine?

If the charity is voluntary, it is permissible to give it to the woman. However, if it is Zakat, her children are obligated to provide for her, and it is not permissible to give her Zakat for her sustenance if she is sufficiently provided for by her children. It is permissible to give her Zakat under another description, such as if she is in debt, or if her children do not provide her with enough and she is unable to obtain it from them.