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 2 (A grandson (from the son)) Number 1 -Does the deceased have female relatives who are entitled to inherit : (A wife) Number 1 - The will which the deceased left behind and that is related to his inheritance is : his eldest son and the grandson:50% and 50% his wife and another son:0% - Additional information : all of them are not muslims but the grandson is a muslim

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 you mean that the deceased and his heirs are all non-Muslim except for his son’s son, the deceased’s estate should be divided among his non-Muslim heirs only and we do not know how it should be distributed according to their laws, whether they are from the People of the Book or not. However, if they referred the case to a Sharee‘ah-court and demanded the application of the Islamic inheritance laws, scholars held different opinions as whether to their request should be fulfilled or rejected. Some believed that it is not obligatory to fulfill their request in this case. This is evidenced by the verse that reads (what means): {… So if they come to you, [O Muhammad], judge between them or turn away from them. And if you turn away from them – never will they harm you at all. And if you judge, judge between them with justice...} [Quran 5:42]

On the other hand, the other scholarly view suggests that in such a case, their request must be met and the Sharee‘ah law should be applied to their case. Allaah, The Exalted, says (what means): {And judge, [O Muhammad], between them by what Allaah has revealed…} [Quran 5:49] They believed that the latter verse abrogated the former.

Ibn Qudaamah wrote, “If non-Muslims living under Islamic rule referred their cases and disputes to us, requesting the application of the Islamic Sharee‘ah, or disputes arose among them, the Muslim ruler is entitled either to judge between them according to the Sharee‘ah or refuse to do so, regardless of whether they are of the same religion or of different religions. This is the opinion of Ahmad and An-Nakha‘i and one of the two opinions of Ash-Shaafi‘i. Abu Al-Khattaab attributed another opinion to Ahmad which suggests that the ruler is required to judge between them. This is Ash-Shaafi‘i's other opinion and the one adopted by Al-Muzani . Allaah, The Exalted, says (what means): {And judge, [O Muhammad], between them by what Allaah has revealed…} [Quran 5:49] Also, the Muslim ruler is obliged to give the wronged person his due right; accordingly, he is obliged to judge among them in such a case, just as he is obliged to judge between the Muslims when disputes arose among them. Allaah, The Exalted, says (what means): {… So if they come to you, [O Muhammad], judge between them or turn away from them...} [Quran 5:42]

Thus, Allaah gave him the choice either to meet their request and judge among them according to the Sharee‘ah or reject their request. There is no disagreement among scholars that this verse was revealed in relation to the Jews of Madeenah, with whom the Prophet, sallallaahu ‘alayhi wa sallam, signed a peace treaty. They requested the Prophet, sallallaahu ‘alayhi wa sallam, to give his judgment on some disputes that broke out among them. That is also because the two disputing parties are non-Muslims; so it is not obligatory to judge between them, as [with] those non-Muslims who are bound with a treaty with Muslims. The verse which they cited as evidence can be interpreted as referring to the case when one  (i.e. the Muslim ruler) chooses to judge between them. Allaah, The Exalted, says (what means): {… And if you judge, judge between them with justice…} [Quran 5:42] Thus, we can reconcile between the two seemingly contradictory verses. We should not opt for the abrogation rule as long as one of the texts can be understood in the context of the other. If this principle is established (and the Muslim ruler is considered obliged or entitled to judge their disputes), it is incumbent on him to judge between them by the law of Islam only.” [Al-Mughni]

The Maaliki scholar Ad-Dardeer wrote, “If the disputing parties are non-Muslims, from the People of the Book or not, and they accepted the judgment of Islam, and both parties gave their consent to that, then our laws should be applied; otherwise, their request should be declined.” [Ash-Sharh Al-Kabeer]

As for your question, if the deceased made a bequest in favor of his son’s son to be given half of the estate, this is a valid bequest because he (the son’s son) is not among the eligible heirs entitled to inherit from him. However, it applies to one-third of the estate only. If he made a bequest in favor of one of his sons to be given the other half of the estate, this is an invalid bequest because it is a bequest in favor of an heir entitled to inherit. In such a case, the bequest should not be executed except with the consent of the other heirs.

As for excluding his wife and the other son from inheritance, this is considered an invalid bequest because it is a bequest to deny an eligible heir his due share of the estate.

Hence, the son’s son gets one-third of the estate, the wife gets one eighth of the estate and the residue of the estate is equally divided among the two sons by virtue of Ta‘seeb (i.e. by virtue of having a paternal relation with the deceased and not having an allotted share, so they get what is left after the allotted shares have been distributed).

Thus, the estate should be divided into twenty four shares; the son’s son gets one third (eight shares), the wife gets one eighth of the residue (two shares), and each son gets seven shares.

It should be noted that the division of inheritance is a serious and critical matter. It is not adequate to settle for seeking an online Fatwa on the matter. Instead, you should refer the case to a Sharee‘ah-court for investigation; perhaps other eligible heirs entitled to inherit would be discovered in the process. Moreover, perhaps the deceased has left a will or was liable to debts or other rights of which the heirs are not aware. It is well-known that the repayment of the debts and the liabilities should be given priority over the heirs’ right in the estate. Therefore, you should not divide the estate among the heirs without referring the case to a Sharee‘ah-court, if any, in order to secure the interests of both the living and the dead.

Allaah Knows best.