The person on the phone with Ashley is Koi (Connor), his husband. They are Grayson's parents. Koi is a dominant omega ans gave birth to 6 kids: Nathaniel, Grayson and Stacy (twins), Chase, Larien and Bliss. All the boys have their own novels (including their parents Ashley and Koi) and we have a manhwa adaptation too for Chase's novel. The 2 girls don't have their own stories, unfortunately.

how does yeonwoo know ashley miller? i dont remember him at all in kiss me liar