Such a question requires a second question prior to answer: is the brother alive or deceased?
A Last Will & Testament becomes effective only upon the death of the person making that Will. A person who has made a Will has the right to change it anytime prior to his or her death, assuming that the person has sufficient mental capacity to make a new Will. As such, a Will cannot be ‘opened’ prior to a person\’s death, as the current Will document may not be the LAST will document that the person can make.
(And certainly, a person has absolutely no “right” to see the Will document of another who is still alive, family member or not.)
If the brother has already died, then family members can review the content of the Will as the probate process is administered.
To create a valid Last Will and Testament easily and affordably, see Standard Legal’s Last Will and Testament legal forms software.