Musannaf Ibn Abi Shaybah 33346 — A husband, a mother, brothers

And he added to it: News has reached me from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that he used to declare the grandfather to stand in the place of the father, so that he would not make a brother an heir in his presence. He would give the husband half of the estate, the grandfather one share, meaning one sixth of the estate, and the mother one third of the estate, meaning two shares.