In a perfect world, estates would never be disputed. The grantor would create his or her will early in their life and proactively manage it, ensuring that beneficiaries are properly designated and that they are receiving what they should get. The beneficiaries would understand the legal complexities of the situation. And, in general, there would be no feelings of anger or resentment based on what the beneficiaries receive.
However, this does not always happen. Estates are disputed and people mount legal challenges. They may do this legitimately or they may do it as an emotional reaction. Either way, there are important legal aspects to consider when an estate is dispute or legally challenged.
A person may challenge a will if there is fraud or forgery suspected. This could happen if the will was manipulated by another party, or if they created a fake will. There is also the possibility that the grantor lacked the testamentary capacity to create the will, which would mean that the grantor was incapacitated or didn't understand what he or she was doing when he or she created his or her will.
Now, wills usually stand up on their own. Rarely are challenged estates overturned. However, there are circumstances where a will can be overturned. Estate disputes are often contentious affairs and they necessitate legal representation. If an estate dispute has been filed, then you need to consult with an attorney as soon as possible.
Source: FindLaw, "Reasons to Challenge a Will," Accessed April 20, 2017