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 is His slave and Messenger.
It is not permissible for a man to make a will so that his inheritance will be divided between his sons and daughters equally, and he is not permitted to make a will to prevent some heirs; if he makes a will to any of the above, his will is void unless all other heirs agree to it. It is the will of Allaah that is more worthy to be applied; Allaah Says (what means): {Allaah instructs you concerning your children [i.e. their portions of inheritance]: for the male, what is equal to the share of two females.}[Quran 4:11]
The will for preventing some heirs or making the share of the female like the share of the male –if this is due to being discontent with the division made by Allaah, or believing that there is some injustice in it to the female – should not be implemented in order to treat him against his will. Moreover, it is feared that such a person would become a non-Muslim because of holding such a belief and not being content with the Ruling of Allaah. Indeed, Allaah threatened those who transgress His Limits in inheritance Saying (what means) {And whoever disobeys Allaah and His Messenger and transgresses His limits- He will put him into the Fire to abide eternally therein, and he will have a humiliating punishment.}[Quran 4:14]
For more benefit, please refer to Fatwa 96941.
Allaah Knows best.