Very few wills are actually contested in probate court. However, the chances of a legal battle over a will go up, when the estate is valuable. It also goes up, if family members do not get along for other reasons.
One of the main reasons that people hire estate planning attorneys is to prevent their families from fighting over their estates after they pass away. People want the attorneys to create estate plans that, if not completely unchallengeable, are at least airtight enough to minimize the possibility of challenges.
The reality is that for any random person, the overall likelihood of a will being contested are relatively small.
As Financial Advisor points out in "Strife After Death"{: target="_blank"} only about 1 in 10 wills are contested. However, for some people, the likelihood of a will contest is much greater than that.
Perhaps the biggest thing that can make a will contest more likely is the value of the estate. The more money there is to fight over, the more likely it is that people will fight.
The possibility of winning a contest to a valuable estate makes the expense of the contest more likely to be seen as worthwhile.
Will contests are also more likely, if family members do not get along for other reasons. People who are at odds over other issues, often find that they are at odds over the divisions in the estate.
This is especially true, if people are surprised by the details of the will and do not think they received as much as they deserved.
While some will contests might be inevitable, going to an estate planning attorney is still the best way to minimize their likelihood. The attorney can provide advice on how to do so.
Reference: Financial Advisor (Dec. 15, 2017) "Strife After Death"{: target="_blank"}