Is it permissible to give zakat to the husband who is ill, expatriated, unemployed, and in debt, or to the brother who is building and does not have enough, or to the sister who is in debt and needs to pay it off?

It is permissible to give zakat to a poor or indebted husband, and to a brother under two conditions so that he may complete building his house. As for your sister who is in debt: if she is able to pay off her debt, then it is not permissible to give her zakat, but if she is unable, then it is permissible.