What are the rights of a married sister over her brother, and is it permissible for her to ask him to buy things without paying for them under the pretext of brotherhood, especially if these things are brought from outside the country?

A sister has the right to be dutifully treated by her brother through good words, visits, gifts, and charity if she is poor. Her maintenance may become obligatory upon him if she is unmarried and he is capable. A married sister's maintenance is the responsibility of her husband, but the brother may still connect with her through gifts and charity.

If a sister commissions her brother to purchase something, the price is her responsibility, unless her brother willingly chooses to cover part or all of it. It is not permissible for her to request this from him as a gift, intending to obligate him out of shame. Whenever she knows that he refrains from demanding payment from her due to shyness, it is forbidden for her to refuse to pay the price, because a Muslim's wealth is not lawful except with his willing consent. Refusing to pay in this situation makes her unlawfully taking her brother's money. Usurpation (Ghasb) is of two types: usurpation by seizure and usurpation by shyness, and both are forbidden.