The elderly can be at risk from unscrupulous people who attempt to claim the estate through marriage, as Wills, Trusts & Estates Prof Blog recently discussed in the article "Challenging Mental Capacity in Marriage."
It is easier to get married than to have someone create a new will. Therefore, people who wish to challenge the inheritance must somehow prove the marriage was invalid. This can be difficult to do, as the burden of proof is on them.
The normal method for a successful challenge is to claim that the elderly person did not have the mental capacity to get married. Just as a will requires mental competence to be valid, so does a marriage, although the mental capacity requirements are not exactly the same for both.
While courts are often sympathetic to those seeking to challenge these types of marriages, it is still difficult to provide the necessary evidence to win.
The expertise of an estate planning attorney can be helpful in such cases.
Reference: Wills, Trusts & Estates Prof Blog (Oct. 22, 2016) "Challenging Mental Capacity in Marriage."