Musannaf Ibn Abi Shayba 26:226

Ibn Fudayl narrated to us, from Bassam, from Fudayl, from Ibrahim, regarding a woman who left behind her sister (from both parents) and her grandfather: The sister (from both parents) gets half, and the grandfather gets half, according to the opinion of Ali and Abdullah. Zayd used to give the sister one-third and the grandfather two-thirds. Abu Bakr said: So this, according to the opinion of Ali and Abdullah, is out of two shares, and according to the opinion of Zayd, it is out of three shares.