Whether or not it is "ethical" to read a parent's will without him or her knowing it is really a matter of how you look at the situation. In most cases, wills are not sealed documents. While they may be private and personal, they are not "off limits." In fact, when educating people about wills and other estate planning documents, Cooperative Extension educators often recommend that these items be discussed and shared with family members so that they are aware of the will creator's wishes prior to death.
That said, it is probably important that you let your parents know you "found" this copy of their will and that you have or have not read it. Disclosing this information could provide a nice opening for a family discussion about estate planning topics.
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