Is the brother obligated to cover the expenses of his deceased brother's daughter and her mother, or only the daughter? What is the specified duration for this, and what is the amount of the expenditure, given that the father refuses to provide them with any expenses?

If the deceased left an inheritance, the daughter and wife should spend from their rightful shares. However, if he did not leave enough to suffice them, then the daughter's maintenance becomes incumbent upon her capable grandfather. The grandfather alone is responsible for her maintenance according to the Shafi'is and in one narration from the Hanbalis, while according to the Hanafis and Hanbalis, it is incumbent upon both the grandfather and the mother. As for the wife's maintenance, it is incumbent upon her capable living father. If he is not present, then it is incumbent upon her capable heirs in proportion to their inheritances according to the Hanafis and Hanbalis, or upon the closest male relative according to the Shafi'is. Maintenance is incumbent as long as they are poor, until they become self-sufficient. The questioner's father must provide for the poor daughter, and the questioner is not obligated to provide for them unless it is a voluntary act, which is a great kindness.