How is Ahmed's estate to be divided among his paternal grandfather, his full nephew, and his full niece?

If the heirs are limited to those mentioned, then the inheritance is exclusive to the grandfather alone, and he takes all the money. This is because he is an asabah (agnate heir) by himself, and there is no sharer (Dhawu al-furud) or closer asabah with him. The nephew (son of the brother) is completely excluded by the grandfather, and the niece (son of the sister) is not an heir at all. Inheritance cases must be submitted to the Sharia courts for investigation, as there might be wills, debts, or rights that take precedence over the rights of the heirs.