Reviewing your data
Don't assume that all vital records are correct. In looking over my grandmother's death record, I noticed that her mother had an incorrect surname listed. The informant was her son in law and apparently he did not know her correct surname. The same error was found in my great grandfather's death record: I believe when the informant (a son in law) was questioned about his (gr-grandfather's) mother, he gave the name of his wife instead.