Who receives priority for sustenance when a grandfather and a brother are present?

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The sound opinion is that the grandfather is prioritized because he has the distinction of lineage and parenthood. Furthermore, the son of the son inherits like a son, whereas the brother inherits like a brother, and the inheritance due to a son is stronger, making the sustenance obligation derived from that status stronger. If the brother is replaced by a son of the brother or an uncle, the grandfather is prioritized in all circumstances.