Division of inheritance among a father, a mother, a wife and one son
29-9-2014 | IslamWeb
Question:
Assalaamu ‘Alaykum; Please calculate the inheritance according to the following information -Does the deceased have male relatives who are entitled to inherit: (A son) Number 1 (A father) (A full brother) Number 1 (A full paternal uncle) Number 1 (A cousin from a full paternal uncle) Number 1 -Does the deceased have female relatives who are entitled to inherit : (A mother) (A wife) Number 1 (A full sister) Number 1
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If the deceased did not leave other heirs entitled to inherit except those mentioned in the question, then the deceased’s mother gets one-sixth of the estate as a fixed share and the father gets one-sixth as a fixed share as well because the deceased left behind a child entitled to inherit. Allaah, The Exalted, says (what means): {And for one's parents, to each one of them is a sixth of his estate if he left children.} [Quran 4:11]
The deceased’s wife gets one-eighth of the estate as a fixed share because the deceased has a child entitled to inherit. Allaah, The Exalted, says (what means): {. . . but if you leave a child, then for them [i.e. the wives] is an eighth of what you leave, after any bequest you [may have] made or debt.} [Quran 4:12]
The residue of the estate is given to the son by virtue of Ta‘seeb (i.e. by virtue of having a paternal relation with the deceased and not having an allotted share, so he gets what is left after the allotted shares have been distributed). The Prophet, sallallaahu ‘alayhi wa sallam, said: “Give the Faraa‘idh (the shares of the inheritance that are prescribed in the Quran) to those who are entitled to receive them; and whatever is left is for the closest male relative.” [Al-Bukhari and Muslim]
The deceased’s sisters, brothers, and the other heirs mentioned in the question do not have a share in the inheritance because of the presence of the deceased’s son or his (the deceased’s) father. Ibn Al-Munthir 
wrote, “Scholars unanimously agreed that the brothers and sisters, whether they are full siblings or from the father only, do not inherit if there is a son or if there is a son’s son (grandson), no matter how far the line of descent extends, or if there is a father.” [Al-Ijmaa’]
Thus, the estate should be divided into twenty four shares. The mother gets one-sixth of the estate (four shares), the father gets one-sixth (four shares), the wife gets one-eighth (three shares), and the residue is given to the son (thirteen shares).
Allaah Knows best.