Ah, Dairy King, while I can't prove anything, I do have a letter from Nintendo I sent concerning this very same topic.
It's postmarked "Jul 11'95", as you can see, it's been a bit of time since then. Anyway, I'll give you the paragraph concerning it:
"Donkey Kong Jr is in the game Donkey Kong for Game Boy, but not in Donkey Kong Land (which by the way, has just been released). According to the best sources, Cranky Kong is the original Donkey Kong. The main character in Donkey Kong Country, Donkey Kong, was previously known as Jr., but he gave up that title when he felt he'd outgrown it. It seems it's hard to be King of the Jungle when you've got 'Jr.' hanging onto the end of your name."
- the 'Jr.' in the paragraph above was changed from "Jr." in the actual letter due to my putting the whole paragraph in quotations.
Believe me or not, I don't care. But I don't think I could make up something as corny was that. Anyway it's signed by:
Yvette L. Kirby
Consumer Service Representative
I can actually remember writing that letter, asking that question. My, how time has passed.