Why is the share of a daughter one half that of a son? Does this mean that sons occupy more importance than daughters? This issue too needs to be understood in its proper perspective.
It is a universally acknowledged fact that the extent of help and co-operation which a person receives from his parents, children and other similar relations has little chance of being paralleled by any other association. Undoubtedly, the world has always considered the kith and kin of a deceased as the rightful beneficiaries of the wealth he has left behind. But certain issues in this regard have always remained unresolved; for example, who among the kindred is nearest with respect to the benefit he holds for the deceased? And how should the inherited shares be ascertained on this basis? In this matter, the extent to which the human mind has faltered and stumbled can be seen from the history these frequent blunders have continued to make. It is not that human endeavour in this regard has fallen prey to any lack of application; rather it is due to certain inherent limitations of the human mind which have made the task itself beyond its reach. Love, hatred, prejudice and other emotions have made it impossible for human intellect to come to grips with this challenge. Consequently, the Almighty Himself has guided mankind in this affair to relieve an Islamic society from the disorders which have originated on this account:
آبَآؤُكُمْ وَأَبناؤُكُمْ لاَ تَدْرُونَ أَيُّهُمْ أَقْرَبُ لَكُمْ نَفْعاً فَرِيضَةً مِّنَ اللّهِ إِنَّ اللّهَ كَانَ عَلِيما حَكِيمًا (11:4)
You know not who among your children and parents are nearest to you in benefit. This is the law of God. Indeed, God is Wise and all-Knowing. (4:11)
It is clear from the above quoted verse that the law of inheritance as stated in the Qur’ān is based on the underlying cause of “the nearest in benefit”, as indicated by the words تَدْرُونَ أَيُّهُمْ أَقْرَبُ لَكُمْ نَفْعاًلاَ(you know not who among your children and parents are nearest to you in benefit). Consequently, the directive in reality does not pertain to the relatives but is related to the underlying cause present in this relationship, which actually entitles them to become the heirs.
Thus the basic reason why the share of a son is more than that of a daughter is the fact that in the life of parents the son is usually more beneficial to them than the daughter. This is so simple a fact that it can be easily understood in societies where the institution of family is still very strong and has deep roots. In a family system, parents become dependent on the children as they grow old. The ease and comfort they feel in living with a son is much more than what they feel while living with a daughter. The simple reason is that a son is independent in taking decisions while a daughter, once she gets married, is actually more dependent on her own husband and is not so independent. The modern western mind feels averse to this distribution because the family system is dwindling in their society.
One thing which may be worth mentioning here is that there may be cases even in societies having a strong family system where a daughter may prove more beneficial to her parent(s) than the son; similarly, there may be cases in which a daughter may require more monetary help because of her circumstances. This can of course be true for a son as well. In such cases, there is a provision that a daughter or a son be given more wealth through a will made in their favour. This will, it is clear, is not on the basis of one’s kinship with the deceased for if it is regarded so, it will alter the divine shares; this will is on the basis of some need of an heir. As per another provision in Islamic law a parent, in his lifetime, can gift as much wealth as is deemed necessary to a child.
In short, the 2:1 ratio pertains to normal circumstances; in exceptional ones there exist remedies in the Islamic law – some of which have been explained above.
Lastly, this difference of share is among the children only since the difference in benefit exists. On the other hand, as far as receiving the inheritance of a child is concerned, in most cases stipulated by Islamic law, both the mother and the father receive an equal share (ie one sixth) because for a child the benefit from a mother and a father is equal.