Yes it is possible to contest the validity of a will. That's a tough burden to meet. You'll have to show that you mother did not have sufficient mental capacity at the time she prepared the will. You'll have to present medical evidence to support that contention. Barring a mental incapacity, your mother is free to divide her estate as she wishes, whether that is perceived to be "fair" or not by her beneficiaries.
Answered on Mar 17th, 2017 at 11:29 AM