Does the presence of a nephew make the mother inherit one-sixth instead of one-third, due to the issue being considered as if there were multiple siblings?

The mother receives the full one-third due to the absence of a group of siblings. The nephew does not reduce the mother's share from one-third to one-sixth. Al-Mawardi Al-Shafi'i stated in "Al-Hawi Al-Kabir" that nephews do not reduce the mother's share, unlike fathers and grandchildren. The difference between nephews and grandsons in terms of reduction is threefold:

1. The term "brothers" does not apply to nephews, whereas the term "sons" applies to grandsons.

2. Nephews are weaker in conferring residue upon their sisters and reducing the mother's share, unlike their fathers and grandsons.

3. Children are stronger in terms of reduction than siblings; they reduce the shares of the husband and wife along with the mother, unlike siblings.