
Josh, I the bodyguard Yeonwoo meets in the garden during a party (chapter 29 I think). That should also happen here too, in the next 1-2 chapters of Kiss me if you can. He meets him later again, and send his friend Dane to help him. you also see him in the side stories. He is Emma's ( Keith's secretary) older brother,
Chase Miller is the actor Keith has problems with after changing his role to a villain role. We only see him once as they talk about him. He is actually at that party, Josh is member of his bodyguard team, but they don't show him in KML. He is also one of Grayson Miller's, Keith's best friends, younger siblings.

We also know that Chase and Josh have 3 children in the side stories
And you can read it alone, there are just some background informations that are missing. I mean there are even more novels of the family and this universe, you can read it without, you just know less.
It's only that "Kiss me liar" and "Kiss me if you can" take place around the same time, so the times Josh meet's Yeonwoo in KLM will also happen in KMIYC, and that movie Chase is shooting is the movie for Keith's production firm during KML.
guys where were these people in kiss me liar?