What is the religious ruling on a will that some siblings believe has wronged them?

If a father bequeaths less than one-third of his wealth to a non-heir, the will is valid and commendable, and not considered unjust; because of the Almighty's saying: (Prescribed for you when death approaches one of you, if he leaves behind wealth, is to make a bequest to parents and next of kin in a reasonable manner – a duty upon the righteous). The obligation of making a will for parents and next of kin has been abrogated by the verses of inheritance, but its commendability remains for non-heirs. A will becomes unjust if it exceeds one-third or if it is for an heir; in such cases, it is not executed except with the consent of the heirs. If a father favors some of his children in gifting without a legitimate religious justification, this is injustice.