Animation Source Forums

And how is that?

Pretty much, Alkan. Frankly, it was a stupid idea on their part, but that's just my opinion.

Each to their own. Domestic licensed products (like 6NA) mixed with the typical lack of continuity always seen in animated movies, lead to confusion.

By domestic licensed product, I mean that a company purchased a license to use so many trademarks from Disney. When they decided they wanted a cub in the stories, it is thought Disney told publishers that Simba could not be used. Probably because Simba is centre to the whole TLK franchise, and if Grolier and their authors made a mess, it wouldn't directly reflect on the character of Simba. So Kopa was created, to give the writers more free rein on the stories, etc. But, the product could then only be sold in the USA, or else it would void the license agreement.

I never gave it much thought. But Kopa will always be non-cannon to me. He is a nice character, but no more real than the fanart creations on DeviantArt.

please read all of this comment before quoting/replying:
from what I've gathered, the cub at the end of TLK (Also known as "fluffy") is supposed to be Kiara, and that disney perhaps made us think it's a boy then say "oh look! It's a girl!"
The TLK6NA books came out just after TLK and were approved of by disney, but they didn't mean for the series to be thought of as canon. In reality, the only cub Simba and Nala had was Kiara, and nothing else can be considered concrete canon. Chaka and/or Tanabi I think were names that disney was going to use for Simba and Nala's child, then Shani when they decided it was a girl, or something along those lines...
BUT
This doesn't mean fans can't use their imagination and use Kopa in their stories or whatnot, as long as they're not arguing all the time that Kopa is definitely canon. (For example, I use Kopa in my fanfic, but know that from disney's point of view, he doesn't exist.) because if we all never wanted to do anything that contradicts disney canon, what would we do comics/drawings/fanfics about?? (This includes Kopa/Vitani)

So anyway, in my opinion, Kopa didn't make it to TLK 2 because disney didn't have it in mind for him. Technically they didn't create him