What is the ruling regarding the inheritance share of the grandfather (Jadd) compared to the father?

Primary text

The grandfather shares the same ruling as the father in three conditions of inheritance. A fourth condition exists specifically concerning the grandfather's relation to siblings, which will be detailed in its proper place. The grandfather is set aside (succeeds to less) because his lineage passes through the father, causing him to be superseded by the father, similar to how brothers are superseded. Every grandfather is superseded by his son due to deriving his inheritance through him. However, the grandfather's portion is less than the father's portion in cases involving a surviving spouse and two parents, or a wife and two parents. In these cases, the mother is assigned one-third of the entire estate, and the remainder goes to the grandfather, unlike the father.