When i first started writing my Novel, i originally planned on writing it like a biography. However since then, i started to see that it was developing into a open world Novel with many characters and subplots. I have two stories about my main character that i planned on writing: One about his childhood in the United States; And the Second, his teenage years in Imperial Germany. But since the story doesn't really have the inciting incident until the third book's ending, i'm now wondering if those two stories aren't necessary. What do you guys think?
If the story doesn't actually start (inciting incident) until the end of the third book, I'm not sure why I would want to read the first two.
You can tell it out of order to move the inciting incident to the front, or to at least move a decision point forward. Then you show how you got there. Of course, you need to steer your scenes to that goal. Think of Fight Club, if you've seen that. It starts with the Ed Norton about to be shot by Brad Pitt. Then the story rewinds to show how he got to that state. We were just having another discussion in a different thread about this trick. I'm not going to bring all that up again. It had to deal with picaresques if you want to search for that. And I mention there that these books where you show a kid coming to be an adult (typically through trial and adversity) are bildungsroman novels. It's a valid genre. I mean, it doesn't get its own shelf at Barnes & Noble, but it's there. Oliver Twist, Anne of Green Gables, Harry Potter, as examples. I've seen Catcher in the Rye tossed in there too, but I always disagree with that. Catcher only covers two days. You need to show a life, not a weekend.
You have to watch histories - sometimes they're great filler rounding out your character's motivation, other times they're vignettes slowing down the plot. I'd consider which items are worth putting in your work and which are better left abandoned.
I think you need to figure out what the story is really about. Is it a particular set of events that take place at a definite period in the chartacter's life? Then you don't need to go into his life story. Most novels don't. But some are really about a person, and their childhood is important in understanding them fully, so parts of it are included. But as with everything, be discriminating about what you include and what you don't. Only include it if it helps advance the story in some way and wouldn't work without it.
Xoic makes a good point here. You often don't need to go into any kind of detail about a character's past. A single sentence is often plenty to contrast an event in the story with the character's past life. Example, the place was a dump, but still better than where he grew up.