Distribution involving a son and daughter of a sister from both parents (Abawayn) and a son of a sister from the mother (al-Umm).
Chapter on Distant Kindred (Dhawu al-Arham)
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
The case is solved from four shares according to those who favor the minority view, and from eight shares according to those who agree with the majority. Muhammad's ruling is as if there were two sisters from both parents and one sister from the mother, solving the case from fifteen shares.
Supporting text
If the offspring of the mother also includes a son and a daughter, the case is solved from eight shares according to all jurists, except Al-Thawri, who grants the male from the offspring of the mother twice the share of the female, solving the case from twelve shares according to him. According to Muhammad, it is solved from eighteen shares.