You seek to have yourself appointed Personal Representative of the Estate as if there was no Will. As a child YOU and your siblings would inherit -- not the common law wife (unless they were legally married, and in some states a common law marriage is recognized as a valid marriage). You would name the common law wife and perhaps her daughter, and you'd better believe that is there was a VALID Will that was favorable to them, the daughter would rush into court with it to prevent you from getting anything.
BUT as this is potentially a tricky matter you really need to GET A LAWYER BEFORE EVERYTHING IS JUST TAKEN AND GONE.