Distribution when a husband, sister, and paternal grandfather are present, and the sister is replaced by a brother and sister, or three sisters.
Chapter on Inheritance of the Grandfather
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
If the sister is replaced by a brother and sister, or three sisters, the paternal grandfather divides the remainder equally with them (i.e., he partakes through المقاسمة (sharing in the residue)).