My nephews renounced their father's estate 10 years ago. Their grandfather passed away last year. His house has just been sold. Can they perceive the share that should have gone to their father?

Yes. Article 754 paragraph 4 of the Civil Code provides that one can represent the person     whose inheritance has been renounced.
Even if the children have renounced the estate of their predeceased father, they can re    present him in the estate of their grandfather.