His statement: “A male or female maternal sibling receives one-sixth; if there are two or more, they share one-third equally.” The evidence for this is the saying of Allah: “If a man or a woman leaves neither ascendants nor descendants but has a brother or a sister, then each one of them receives one-sixth. But if they are more than that, they shall share one-third” [4:12]. That is, if a man or woman is inherited from as a kalālah—one who leaves neither ascendants nor descendants. Allah did not say: “If they are more than that, then the male shall have the share of two females”; rather, He said: “They shall share one-third.” Sharing entails equal division, just as the wording “between you” entails it. Thus, if you were to gift some property to a group and say, “It is to be divided between you,” it would be divided equally: the young and the old alike.
Maternal siblings inherit subject to two conditions: that there be no inheriting descendant and no inheriting male ascendant. If either is present, they do not inherit. Thus, if someone dies leaving a grandfather—his father’s father—and a maternal brother, the maternal brother receives nothing, because an inheriting male ascendant is present.
Likewise, if he dies leaving a son’s daughter and a maternal brother, the maternal brother is excluded, because the case includes an inheriting descendant, namely the son’s daughter. Once their right to inherit is established, one receives one-sixth, while two or more receive one-third, divided equally among them.
There is nothing in the law of inheritance in which males and females receive equal shares except maternal siblings: their males and females are equal. Why? There is an answer to which there can be no objection: this is Allah’s ruling. Allah, Exalted is He, says: “It is not for a believing man or a believing woman, when Allah and His Messenger have decided a matter, to have any choice in their affair” [33:36]. This—meaning Allah’s ruling—is what the Mother of the Believers, Aisha, relied upon when a woman asked her: “Why is it that a menstruating woman…”