Who are the heirs of a grandmother whose only son has passed away, and she has six grandchildren (five boys and one girl), and she has no living brothers or sisters, but she does have nieces and nephews from her siblings?

The grandchildren (sons of the son) inherit their grandmother's estate, with the male receiving the share of two females. The children of the siblings do not inherit in the presence of the children of the son, because the lineage of sonship takes precedence over the lineage of siblingship. As for the children of the sisters, they do not inherit at all.