The Kitáb-i-Aqdas - The Most Holy Book
Index term: half-brothers, under brothers; allocation of shares and property; Inheritance
n39.
to the brothers, five parts . . . to the sisters, four parts
Questions and Answers amplifies the provisions of the law as it relates to the shares of the inheritance allocated to the brothers and sisters of the deceased. If the brother or sister is from the same father as the deceased, he or she will inherit his or her full allotted share. If, however, the brother or sister is from another father he or she will inherit only two thirds of the allotted share, the remaining one third reverting to the House of Justice (Q&A 6). Further, in the case where the deceased has full brothers or full sisters among his heirs, half-brothers and half-sisters from the mother's side do not inherit (Q&A 53). The half-brothers and half-sisters will, of course, be due to receive inheritance from their own father's estate.
q6.
 
Question: Is it necessary that the brother, in order to qualify for his portion of the inheritance, be descended from both the father and the mother of the deceased, or is it sufficient merely that there be one parent in common?
Answer: If the brother be descended from the father he shall receive his share of the inheritance in the prescribed measure recorded in the Book; but if he be descended from the mother, he shall receive only two thirds of his entitlement, the remaining third reverting to the House of Justice. This ruling is also applicable to the sister.
q53.
 
Question: With reference to inheritance, when there are full brothers and full sisters, would half-brothers and half-sisters on the mother's side also receive a share?
Answer: They receive no share.