Successfully contesting a will is not easy. There must be a reason why the court should not accept the will. A common reason is because there was undue influence in the will's creation.
Wills are supposed to be the testator's carefully thought out wishes about who should have their property after they pass away. They are supposed to be made with great care and after deliberation.
When the will is the result of what someone else wants, it is known as "undue influence" as My Prime Time News discusses in "Undue Influence."
Undue influence can happen when someone who benefits from a will encourages the will's testator to create the will for the influencer's benefit. Merely encouraging someone to make a will does not create undue influence.
A common example is one child convincing his parents to leave him more in the will than his siblings. The siblings will be upset and may decide to challenge the will.
If the court does not believe there was a valid reason for the different inheritances, then the court will invalidate it on the grounds of undue influence.
One way to avoid having your will invalidated on undue influence grounds is to hire an estate planning attorney who can ask the appropriate questions to make sure the will you are getting, is really what you want and not what someone else wants.
Reference: My Prime Time News (Jan. 18, 2017) "Undue Influence."