I'm loosely working on a trilogy. Book One and Two are supposed to contain the main character’s backstory, divided by two parts that will be exposed accordingly: on book One, the first half, on book Two, the remaining part.
I have three "main characters", with one being more in display, as the epicenter of the story, than the other two. So character A, the really main one, has a very long, interesting backstory that will need to be exposed (both to the reader and the other characters eventually) to further the story.
A, B and C grew up together. At some point, A goes missing. Book One starts ten years later, when B and C finally reunite with A. My main probably is, by choosing not to tell the story of their childhood and the subsequent years, how will the readers engage with the reunion, not having any attachments to this characters yet?
My worst problem is: how do I tell, along with book One's story, the background of all the years A has been missing without losing pace of the main story?
My initial idea was to introduce this characters childhood in the prologue, giving the reader something to work with, and just do flashbacks throughout the books, telling what I need to tell. But it doesn't sound very engaging, and the reunion of these characters has no actual payoff because the reader won't be really attached to them to care...
Any advices are welcome :)