Musannaf Ibn Abi Shayba 26:217

Abu Mu'awiyah narrated to us, from al-A'mash, from Ibrahim, from Abdullah, that he said regarding a daughter, a sister, and a grandfather: He gave the daughter half, and he made what remained between the grandfather and the sister, for him is half and for her is half. And he was asked about a daughter, two sisters, and a grandfather: He gave the daughter half, and he made what remained between the grandfather and the two sisters, for him is half and for them is half. And he was asked about a daughter, three sisters, and a grandfather: He gave the daughter half, and he made for the grandfather two-fifths of what remained, and he gave the sisters three-fifths.