to a mixed group of male and female grandchildren through a son.
Nothing, however, is allotted to female grandchildren alone unless there is a male beneath them in degree who converts them into residuary heirs.
The children of a grandson stand toward the children of a son as the children of a son stand toward direct children, and the same principle applies to every lower level: a male in a lower generation renders those of his own generation residuary heirs, and he does the same for females in higher generations only if she has taken nothing of the two-thirds.

Section
The father inherits by fixed share when a son or a son’s son is present, by agnation when there is neither a child nor a grandson through a son, and by both when there is a daughter or a granddaughter through a son. In that last case he is entitled to one-sixth as a fixed share and, after their prescribed portions, to the remainder as residuary heir.
The mother is entitled to one-third or one-sixth in the two previous fixed-share situations. In the two ʿUmariyyah cases—those that contain a husband or a wife together with both parents—she receives one-third of what remains after the spouse’s share.
The grandfather stands in the place of the father, except that the father eliminates the brothers and sisters altogether whereas the grandfather shares with them if they are full or consanguine siblings. The father also excludes his own mother, whereas the grandfather does not. Moreover, in the ʿUmariyyah cases the father reduces the mother’s share from one-third of the estate to one-third of what remains after the spouse, whereas the grandfather does not cause this reduction.
A single grandmother receives one-sixth, and the same applies to all grandmothers who qualify. Among them inherit: the mother’s mother and her female ascendants; the father’s mother and her female ascendants; likewise the mother of the father’s father, the mothers of the grandfathers above him, and their maternal ascendants, according to the predominant opinion. The governing rule is that every grandmother whose line to the deceased passes entirely through females, or through males up to a male, inherits; whereas any grandmother whose connection runs through a male situated between two females does not inherit.

Section
If full brothers and sisters are the only heirs, they inherit like direct children, and the same applies to consanguine brothers and sisters—save for the Musharakah case, which consists of a husband, a mother, a uterine sibling, and a full brother: here the full brother shares with the uterine siblings in the one-third. If that brother were consanguine instead of full, he would be excluded.
When the two categories of siblings come together, they are treated like direct children and grandchildren through a son, except that the granddaughters through a son