Is the paternal grandfather considered a father in lineage for the purpose of veiling siblings?
Chapter on Inheritance of the Grandfather
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
The grandfather is considered a father, and therefore he veils the siblings, equivalent to a true father. Proof for considering the grandfather a father is found in Quranic usage such as 'the religion of your father Abraham' (Quran 22:78) and prophetic statements equating tribal ancestors to fathers, such as the statement regarding Ishmael's descendants. This equivalence is further supported by the fact that the son of a son (grandson), no matter how distant, replaces his father in veiling, and similarly, the father's father (grandfather) replaces his son, leading 'Abdullah ibn 'Abbas to question Zayd for treating the grandson as a son but not the grandfather as a father. Since the grandfather shares many rulings with the father due to shared lineage of procreation, he should share in this veiling aspect.
Supporting text
It is noted that the paternal grandfather's lineage relation to the siblings is stronger than that of the mother's siblings (maternal uncle/aunt), as the grandfather veils the mother's children, yet the mother's children do not veil the grandfather, highlighting the grandfather's superior connection via the father.