If your relatives have written a will, they have probably done more estate planning than most of their neighbors. After all, 62% of Americans have no will at all. Having a will, though, does not do your loved ones much good if the document does not reflect their authentic wishes.

Undue influence, where someone plants his or her interests over those of the will’s author, may be grounds to contest a will. Here are three of your close relatives who may be vulnerable to undue influence in the estate planning process.

1. A grandfather who has a live-in caretaker

As individuals age, they often feel a sense of isolation from friends and family members. If your grandfather has a live-in caretaker, he may believe the caretaker should receive some or all of his assets. While it may be acceptable to leave assets to a caretaker, you may want to question whether undue influence played a role in your grandfather’s will.

2. A mother who recently changed her will

If you have a close relationship with her, you may believe you know your mom better than anyone. You may also be able to predict what your mother intends to do with her wealth. If your mom reworks her will and makes seemingly bizarre bequests, you may have a duty to object.

3. A brother who let someone else take control

For individuals with many assets, writing a will can be tricky. Even though your brother may need some help with his estate plan, he probably should not let someone else take complete control. This is especially true if the final will goes against your brother’s interests or the interests of your family.

Even though undue influence can be hard to prove, it is often disastrous. If you suspect someone in your family may be the victim of undue influence, contesting the will may be the most effective way to protect your loved one’s legacy.