Musannaf Ibn Abi Shaybah

Fudayl narrates that Ibrahim said that grandmothers are heirs to one-sixth of the wealth. So, whether there is one, two, or three, the share will be divided among them according to the statement of Ali (may Allah be pleased with him) and Zaid (may Allah be pleased with him). And when three grandmothers gather, each of whom is equally related to the deceased, then one share will be divided among them. These grandmothers are: the maternal grandmother, the paternal grandmother, and the paternal great-grandmother. And Abdullah (may Allah be pleased with him) says that when three grandmothers gather, one-sixth of the wealth will be divided among them, even if none of them is closer in lineage to the deceased, such that none of them is the mother of the other.