Is it permissible for a sister to inherit all the possessions of her deceased brother, who has no heir other than her, despite the existence of his nephews?

A will in favor of an heir is not permissible unless the other heirs agree to it, based on the Prophet's (PBUH) saying: "Indeed, Allah has given every rightful person his right, so there is no will for an heir." If the heirs approve this will, it becomes permissible according to the majority of scholars.

In this case, the sister takes half of the inheritance, based on Allah's (SWT) saying: "If a man dies, leaving no child but a sister, she shall have half of what he leaves." The male sons of the full brother take the remainder equally, without the females, based on the Prophet's (PBUH) saying: "Give the prescribed shares to those entitled to them, and what remains is for the nearest male relative." As for the sons of the half-brother, they inherit nothing.