Musannaf Ibn Abi Shayba 26:225

Waki’ narrated to us, he said: Sufyan narrated to us, from Abu Ishaq, he said: We came to Shurayh and asked him about a husband, a mother, a brother, and a grandfather. He said: "For the husband is half, and for the mother is a third." Then he remained silent. Then he said: "The one who is over his head—he does not say anything regarding the grandfather." He said: So we came to ‘Ubaydah, and he divided it into six according to the opinion of ‘Abdullah. He gave the husband three, the mother one share, the grandfather one share, and the brother one share. Abu Bakr said: This, according to all of their opinions, is out of six shares.