Died leaving a mother, a son, a grandson and a half-brother
21-3-2013 | 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 son of the son's son) Number 1 (A half brother (from his father)) Number 1 -Does the deceased have female relatives who are entitled to inherit : (A mother) - Information about the deceased’s debts : (Debts to people)
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.
The debts of the deceased must be paid before dividing the inheritance as Allaah says (what means): {…after any bequest you [may have] made or debt.}[Quran 4:11]
If the deceased did not leave any other heirs except those mentioned in the question, then his mother gets one-sixth as her legal share due to the existence of his child as Allaah 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 remainder should be given to the son by Ta’seeb (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) as the Prophet 
said: “Give the prescribed share of inheritance to those who are eligible for it and the remainder [of it] is for the nearest male blood relative.” [Al-Bukhari and Muslim]
The grandson and the brother do not get anything from the inheritance because they are prevented by the existence of the son.
Finally, it should be noted that the matter of inheritance is a very complex and serious issue, so a mere Fatwa which is an answer issued according to the question is not enough. Rather, the matter should be taken to an Islamic court to look into the case, or it should be presented orally (in person) to the scholars if there are no Islamic courts. It might be that there is an heir who would not be known except after investigation, and there might also be a will, debts, or other dues that are not known to the heirs. It is known that these rights come in priority over the right of the heirs. Therefore, the inheritance should not be divided without resorting to an Islamic court, if available, in order to fulfill the interests of both the dead and the living.
Allaah Knows best.