It is reported from al-Sha'bi that the inheritance of a mother, a sister, a husband and a grandfather, according to the view of Sayyiduna Ali (may Allah be pleased with him), is: a third for the mother, a half for the sister, a half for the husband and a sixth for the grandfather, out of nine shares. According to the view of Sayyiduna Abdullah (may Allah be pleased with him): a half for the sister, a half for the husband, a third for the mother and a sixth for the grandfather, out of nine shares; and the grandfather combines his sixth with the sister's half, so the grandfather gets two thirds of it and the sister a third. Nine is multiplied by three, making twenty-seven: six for the mother, nine for the husband, and of the remaining twelve, eight for the grandfather and the remaining four shares for the sister. This is al-Akdariyyah, umm al-furuj.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12447