There are sometimes occasions where people express interest in drafting an Islamic Will; they then go into detail about what they want, and it becomes clear that it is not actually an Islamic Will at all.
The most common way that this situation presents itself is through parents wanting to divide their estate equally between their sons and daughters. According to the Mawarith Schedule in the Qur’an (what Islamic Wills are based on) the sons and daughters would inherit at a 2:1 ratio, with the sons inheriting double what the daughter would. Regardless of what the testator wishes, for a Will to be Islamically compliant it must follow the rules of the Mawarith Schedule.
In short, a minimum of 2/3 of an estate must be distributed in accordance with the Mawarith Schedule of the Qur’an (Surah an-Nisa). The remaining 1/3 can be gifted in accordance with the wishes of the testator. Often individuals will seek to distribute the 1/3 ‘gift’ portion of their estate in a way that would ‘even out’ the distribution amongst their children.
It is agreed by all 4 madhabs (Islamic schools of thought) that if an individual wishes to give a gift from the 1/3 portion to an individual already receiving under the 2/3s dictated by the Mawarith schedule, they must gain agreement from the other beneficiaries receiving under the Mawarith Schedule at the times of execution and distribution of the estate. If any of the beneficiaries have objections to the gifting, then the distribution must be recalculated in a way that their portion will remain as if the beneficiary to be gifted was not receiving the gift from the 1/3. However, an objection at the time of distribution creates legal issues as the contents of a properly drafted Islamic Will cannot be altered and are legally enforceable in Australia.
In the end, it is possible to evenly distribute your estate amongst your sons and daughters evenly while also keeping your Will compliant with Islamic Law. However, it will require you to gain the agreement of the inheriting parties and trust that they will maintain their agreement when it comes time for distribution.