Musannaf Ibn Abi Shayba 26:224

Ibrahim said regarding a woman who left behind her husband, her mother, her brother from her father, and her grandfather: For the husband is the half, which is three shares; for the mother is the third, which is two shares; and for the grandfather is one share, according to the opinion of Ali and Zayd. According to the opinion of Abdullah, for the husband is the half; for the mother is a third of what remains, which is one share; for the grandfather is one share; and for the brother is one share. If there were two brothers or more than that, then for the husband is the half; for the mother is one share; and for the grandfather is one share. The remaining share belongs to his siblings, according to the opinion of Ali, Zayd, and Abdullah.