Chapter on the Inheritance of Full Sisters
Allah—exalted be He—has set out the shares of full sisters and paternal sisters, whether each is alone or they appear in a group, in His words at the close of Sūrat al-Nisāʾ:
“They ask you for a ruling. Say, ‘Allah gives you a ruling concerning al-kalālah: if a person dies leaving no child and leaves a sister, she shall have one-half of what he left; and he shall inherit from her if she leaves no child. But if there are two sisters, they shall share two-thirds of what he left; and if there are brothers and sisters together, the male shall receive the share of two females.’”
He also mentions the inheritance of uterine brothers and sisters—whether one or more—in the opening of the same sūrah:
“If a man or a woman dies leaving al-kalālah and has a brother or a sister, then each of them shall have one-sixth. But if they are more than that, they shall share one-third.”
A full sister is entitled to one-half of the estate when four conditions are fulfilled:
Condition 1: The absence of her male agnate of equal rank, namely a full brother, for Allah says, “If there are brothers and sisters together, the male shall receive the share of two females.”
Condition 2: The absence of a co-sharer of her own class, namely another full sister, as indicated by His saying, “If a person dies leaving no child and leaves a sister, she shall have one-half of what he left; but if there are two sisters, they shall share two-thirds of what he left.”