Classification of heirs based on their manner of inheritance.
Chapter on Who Inherits from Men and Women
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
All heirs fall into two categories: those with fixed shares (dhawu furud) and residuaries (asabāt). The male heirs are all residuaries, with the exception of the husband, the uterine brother, and, when a son is present, the father and the grandfather. All female heirs are those with fixed shares when they are alone without brothers, with the exception of the freedwoman, and when sisters are present with daughters.
Supporting text
The specified residuaries among males include the son, his descendants however far down; the father, his ascendants however far up; the full brother, the father's brother and his sons however far down; the paternal uncles and their sons however far down; the father's paternal uncle and his sons perpetually; and the freedman.