Jenna growing up:
[They don't have to be the people I'm using but yes]
Something like those: [I have no idea who they are though lmao]
But of course, adult Jenna would be played by Sara Canning:
[I have no idea for who to be young John and Grayson Gilbert (basically Gilbert's) nor for the Sommer's, nor Mason but whatever I guess]
Adult Mason Lockwood
But as young Taylor Kinney here-
Narelle is played by Emilia Clarke