As Johnny Boy didn't point it out, there is an "edit" button at the top right of your post that you can use to make adjustments when need be, rather than posting again.
Anyway, onto the topic of Kovu, here are my thoughts on him:
He was born
after Scar's death. A lot of fans believe Zira's ludicrous claims that he was hand-chosen by Scar to take his place as king but honestly, that's just not chronologically possible, and Zira's character puts her as very likely to lie and make things up to suit her needs. Based on Kovu's size when he and Kiara first meet and meet again later on, the development of his mane, and his mental state throughout the movie, Kovu can't be significantly older than Kiara. A month or two, sure, but given the amount of time it would take the land to recover from the drought and for Kiara to be born, Kovu would be a lot bigger than she is if he were born while Scar was alive. He'd be Nuka's age or so. This obviously isn't the case, and therefore, it stands to reason that Kovu cannot have been hand-chosen by Scar. (Unless, as I jokingly suggested once before, Scar returned as a ghost, like Mufasa had, and chose his heir.)
I do believe Kovu
is Zira's own cub. Many theories have him adopted from some other lioness (usually kidnapped), but I don't think so. Zira wouldn't see spawn that were not her own as worthy of being Scar's heir. I fully believe that all of her children are biologically hers and not Scar's. Kovu at least is not Scar's, as the movie says so twice. I believe that he was inherently good, despite what some think, because he was eager to befriend Kiara as a cub and an adult. His switching of sides was too quick (even if you go with my theory that there were several days that weren't shown while he was at Pride Rock before the ambush (it just doesn't make sense otherwise)) for him to have been truly intent on killing anyone. The same seems to apply to his sister Vitani, and it's possible that their father was a good-natured lion, and/or that Zira was goodhearted herself before snapping and going totally insane.
Kovu also strikes me as underdeveloped, as do most of the characters introduced in this film. He follows what his mother tells him until he loves Kiara, then he is almost blindly good. They tried to give him depth of character by giving him similarities to Scar, but it was so barely touched on that it didn't really stick. Kovu stands out as his own character, not one nearly as powerful as Scar, and too much of a goody-two shoes to be like him. This is not to say that I dislike Kovu, because I certainly don't! It's simply that they didn't devote enough time to making the character emotionally complex, in my opinion.
I have a lot of gripes with SP in general, but I do love it, all the same.