When a person promises to give a certain inheritance to another person and breaks that promise in a will, it is possible to challenge the will. If the existence of the promise can be proved, courts might uphold it if they find it is legally binding. One case in Australia illustrates that, but it is unusual because of the nature of the promise.
Court documents in Australia tell the story of a woman who was sexualy abused by her father beginning at the age of 14 and the abuse continued for nearly a year. The woman told her mother who promised to put an end to it. The Age Victoria reported this story in "Woman sues mother over inheritance after keeping father's sexual abuse secret." For her part, however, the mother refused to leave her husband and asked the daughter not to inform the police.
The mother's reasoning was that the couple was putting together a large estate and if she left the marriage, her daughter would not get any of it. In exchange for not telling authorities about the abuse, the mother promised the daughter half of her estate.
Many years later, when the mother passed away, her will broke the deal. She left the daughter only 33% of the estate. The mother also cut the daughter's son out of the will completely because when he was five he too was abused by the same man and instead of remaining quiet he told the authorities. The woman sued her mother's estate. The Australian court agreed with her position.
It awarded additional funds from the estate be given to the daughter and the grandson. The court reasoned that the mother had a moral duty to protect her daughter and to put her daughter's happiness and welfare before the estate. According to the court, the mother failed in this moral duty and therefore had harmed her daughter in a way for which compensation was deserved.
Reference: The Age Victoria (August 18, 2015) "Woman sues mother over inheritance after keeping father's sexual abuse secret."