I’ve lived all of my 42 years in Michigan and I’ve followed mitten politics since junior high. Nobody here in Michigan—not even some of our most liberal press—considers Mitt a “Michigan native,” regardless of his family ties. He’s too closely associated with Taxachusetts for us to have—or want—any claim on him.
That was not my point but I disagree with your statement nontheless.
I happen to be from Michigan too and most people over 45 remember George Romney well and hence his son Mitt, both were/are considerered favorite sons.