What is the distribution between a grandfather and a sister?
Chapter on Inheritance of the Grandfather
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
When a grandfather and a sister are present, the distribution is based on three shares: two shares for the grandfather and one share for the sister. This configuration is established because partition is more advantageous for the grandfather in this instance.
Supporting text
Ali, may Allah be pleased with him, ruled that the daughter receives half, the grandfather receives one-sixth, and the remainder goes to the sister. Ibn Mas'ud held that the remainder after the daughter's prescribed share is divided equally between the grandfather and the sister, as each would take the entire estate by representation if present alone, thus they divide equally when combined, similar to if a brother were in the sister's place.