So we know that Rafiki is a trusted friend of the royal family because he plays a key role in the presentation ceremony for new cubs and was instrumental in convincing Simba to return to the Pridelands. Also, he seems to perform Kiara and Kovu's "wedding" at the end of SP.
We also see him receive sort of a divine revelation from Mufasa that Kiara and Kovu getting together is the answer to the impending crisis. My question is why didn't he tell anyone? It is understanable that he wouldn't tell Kiara and Kovu directly since those who feel pressured to fall in love rarely do, but why would he not tell Simba, especially when he was bordeline obsessed with living up to his father's legacy? Such a conversation seems like it could have saved a lot of unnecessary trouble.