Do the daughters' children deserve anything from the inheritance of their grandfather, who passed away leaving behind sons of his son and grandchildren of his daughters, especially after the son's son seized the entire inheritance under the pretext that it was from his infidel grandfather?

Since the matter involves dispute and disagreement, it must be referred to the Sharia (definition) court or to a scholar qualified to issue judgments. Muslim grandchildren have no share in the inheritance of their non-Muslim grandfather, according to the hadith (definition): "A Muslim does not inherit from a disbeliever, nor does a disbeliever inherit from a Muslim." As for the inheritance of their father, who died before their grandfather, they do have a share in it, and the brother is not permitted to take it exclusively without his sisters.