A Will should go to Probate, however generally if his Personal Estate was under £15,000 a lot of financial Institutions will pay out against an Indemnity. Some will insist on Probate for much lower amounts. If before death your brother put everything in joint names with his wife, it would all automatically be transferred to her sole name. This is quite common as people get older or ill and want to make things simple for each other.
Of course his widow is not obliged to tell you anything about the Will, although it will eventually be in the public domain. The Executors have a Duty to act in accordance with the Will and beneficiaries may not know they are to inherit anything until it is actually received.