It would have been nice to learn more about their relationship. :)

I feel the same way about Simba and both of his parents in the first film. It would have definitely been nice to see more of him with Sarabi, and I wouldn't have minded a bit more interaction between him and Mufasa too (although I loved that we saw a good amount of them together).

I think what I would have really liked is to have seen more of Simba and Kiara's childhood, in their respective films. That way, we would have likely learned more about their relationships with their parents.