As size of estates increase, so do the number of challenges. However, success isn't easy to come by.
As the number of wealthy estates increase, both the U.S. and Canada find themselves in challenges brought about by people who believe they didn't get their fair share, according to The Globe and Mail in "Left out of the will? Here are your options."
The options for challenging a will in Canada are very similar to those in the U.S. There needs to be a good reason why the court should disregard the will and distribute the estate differently.
A common reason is by citing undue influence. That is the allegation that someone has inappropriately influenced another who has diminished capacity of some sort to create a will for the benefit of the influencer. It is not an easy case to prove, but it is possible to do so.
In the U.S. and in Canada, not just anyone can challenge a will. Only people who have a financial interest of some sort in the estate can make the challenge.
An estate planning attorney can advise you on your various options, if you feel you haven't been treated fairly.
Reference: The Globe and Mail (Feb. 26, 2018) "Left out of the will? Here are your options."