My aunt passed away and left the estate to my wife. However a cousin who was left out was made executor, and items may be missing. what can we do?

My wife's aunt recently passed away after battling cancer for 4 years. An old will was found that left everything to my wife and her brother, however she named a cousin (who had a very bad relationship with our aunt after the will was written) executor but left this cousin nothing. We suspect things have been taken from the home, but can't prove it. Is there a way to have the cousin removed as executor due to conflict of interest? Additionally at what point after the death (after probate?) does my wife and brother in law legally own the estate?