As for as I can come up with, these are indeed different spellings for the same surname. In the case of Louisiana ancestors, many of the federal officials with the census only knew English, but majority of our Louisiana ancestors only know Cajun-French. So, when these people traveled down the bayous, they did the best they could to spell these french names. In many cases, it is very close to the original. In others, not so much.
Louisiana has Spanish-French-English influence. And so, as stated above language issues were very much a problem.
Lajeunesse is possible the original surname- (it is a french word meaning Young in English). And I have found Youngs and Lejeunes to be in the same family branch. My guess is the interchangeable French/English Version. Other versions I came across, but I'm not very sure about-Joinie, Jouny, Joineau
This is only my opinion and I do not have physical proof. In my own research (and talking with my 81 y/o father), misspellings and language is a big problem with many families in Louisiana. My Nelton family surname is a misspelling of the original Nettleton surname.
Hope that helps!
|BTW: My Lajaunie Line (starting with my grandmother):
1. Mildred Lebouef (d/o Albert Leboeuf and Sara Lajaunie)|
2. Sara Lejaunie (d/o Mathis Marcelin Ernest Alcee Lajaunie and Marie Eve Authement)|
3. Mathis Lajaunie (s/o Alexander Lajaunie and Emelia Sevin)|
4. Alexander Lajaunie (s/o Francis Lajaunie and Francoise {Bringuie or Brigue)|
Only line 1-3 can be verified at this time.