Haha, weird. I was actually thinking about this earlier today! Well, I was wondering what kind of impact Kion would have had throughout the whole movie, if he'd been in it.

Kion teaches Simba to be accepting and open-minded towards the animals he chooses to join the Lion Guard, which is similar to how Kiara teaches Simba to accept the outlanders in this movie. Obviously, Kiara's personality is very different in The Lion Guard (probably to show contrast between her and Kion), but for now I'm going to assume that, if Kion was in Simba's Pride, he'd be the same character he is in The Lion Guard. In which case he and Kiara would have much more in common. Both mischievous, both adventurous, and both open-minded towards others.

In which case I think Kion would likely not be against Kovu being a part of their pride. I think he'd be more likely to trust Kiara's judgement of Kovu's character. I can kind of imagine Kovu and Kion being pretty good friends during the time Kovu stays at the pridelands too!

Obviously he'd have been concerned when Simba initially came back injured from the ambush, like Kiara was, but I also think that, like his sister, he wouldn't buy into the idea that Kovu was trying to cause trouble. I don't know whether he'd have run off after the exile to try and find Kovu, but maybe instead he'd have stayed behind and tried to talk Simba into changing his mind if Kiara brings Kovu back.

I know Kion was born after the events of The Lion King 2 in my theory, but, if he was present during Kovu's exile, then he would help the lionesses back.

i would stop my dad i would exile myself