Who’s a Cajun?  That depends on who you ask and when you ask them.  The Sociological Images blog has a very good summary of an article on this topic, Cajun: From Disparaged to Delicious.   Turns out ethnic identification changes over time.  People who identify themselves as Cajun have increased since Cajuns became cool.  We all saw the surge in Cajun music and food in the 1970s and 1980s, continuing to the present.  Comic strips joke about how hot Cajun food is, and everybody’s heard of Cajun music (though often not understanding what it is and isn’t).   This all comes from the 2002 book Blue collar bayou: Louisiana Cajuns in the New Economy of Ethnicity.   Find it in your local libraries in WorldCat.org.   There are other books and articles on the subject.  Might be time to start that Cajun/Creole/zydeco bibliography.   See what Google Books has.