Do you think that undue influence caused a parent to create a will or estate plan that didn't actually go along with what he or she would have wanted? If so, one thing to carefully consider are the medical records for that parent. They can strongly support your case.
For instance, perhaps your parent was suffering from a degenerative brain disease, like Alzheimer's. You even had to move the parent into a home. You couldn't visit as much as you would have liked, but a step-sibling -- who wound up getting much more than you in the will -- was there all of the time.
There are also two wills, written five years apart. The first one gives you and the step-sibling the same amount. The second one, written just a few months before your parent passed away, changes things dramatically, and not in your favor.
You believe that your step-sibling used the Alzheimer's disease to his or her advantage. As your parent's mental health declined, that sibling started lying and pressuring him or her to change the will. It was eventually altered, but your parent wouldn't have done that without this outside pressure. If the medical records shows that the Alzheimer's disease really was getting worse at this time, that may back up your suspicions.
Accusing someone of undue influence is very serious after a loved one's death. It can cause a rift in the family that may never heal. Be sure you know your legal rights and what type of evidence can be used to make sure justice is finally served.
Source: Greater Wilmington Business Journal, "When To Challenge A Will Based On Undue Influence," Andrew Olsen, June 01, 2017