What is the share of the missing paternal uncle and his heirs in the division of the inheritance, and should his share be sent to charities, or taken by one of the heirs, or redistributed among the siblings?

The share of the deceased uncle is not redistributed among the brothers, nor is it sent to charities; rather, it goes only to his heirs. His share must be delivered to his children and grandchildren if you are aware of their existence. If they cannot be found after searching, the matter should be referred to the Sharia court for the judge to rule on their presumed death or continued existence and what follows from that. It is advisable to seek assistance from the American embassy in searching for the heirs.