Basic rules of inheritance
In the Shariah, there are 4 rights on the wealth left by the deceased.
1. Burial expenses.
2. Repaying of debts. If the dower (Mehr) of the wife has not been paid, then this also should be paid.
3. If there is any will about a non-inheritor, then this will be fulfilled with 1/3rd of the wealth left by the deceased.
4. Distributing the remaining wealth among the inheritors as per the guidelines of the Holy Quran and the Sunnah.
As given in Siraji Fi Ilmil Faraaidh, Pg. No. 3 and 4.
First the burial expenses of the deceased should be borne here. If somebody else has borne them, then they should be repaid to that person. If the dower of the wife had not been given, then it should be paid. If other debts are there, they should also be repaid. If the deceased had bequeathed anything to somebody who is not among the inheritors of the wealth of the deceased as recognized by the Shariah), then this will be fulfilled with 1/3rd of the wealth of the deceased.
After this, if there are no other inheritors apart from the mentioned ones, then all the wealth including the plot of land will be divided into 96 equal parts. The wife will receive 12 shares, the daughters 7 each and the sons, 14 each.
Will a Muslim child inherit from non-Muslim parents or vice versa?
If the inheritor and the one from whom he/she is inheriting are of different religions, then as per the Shariah, the inheritance laws don’t come into play at all. There is a Hadith in this regard:
It is narrated on the authority of Hadhrat Usama bin Zaid (May Allah be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: A Muslim cannot be the heir of a non-Muslim and a non-Muslim cannot be the heir of a Muslim. (Sahih Muslim, Hadith No. 4225)
If the parents are non-Muslim, then as per the Shariah, Muslim children of those parents are not their heirs. As far as treatment of parents is concerned, even though they are non-Muslims, the parents should be treated honorably and kindly. They should be served. However, if they command any sin to that extent they should not be obeyed.