Not just anyone might challenge the validity of a Will. State laws vary a little, all require that you be related to the Will in some manner. Normally, you must have the ability to show that you would have received more from the decedent, if she or he had passed away without a Will; or if she or he composed an earlier Will that left you more than the existing Will.
Concern 2: When can I challenge the Will?
Question 3: How can I reverse a Will?