10 Ways Star Wars: The Last Jedi Was Almost Completely Different
3. Finn's Backstory

Originally pegged in The Force Awakens' early marketing to be the next jedi we'd go on some intergalactic adventure with, Finn worked as an allegory for the audience, interacting with different characters and locations, playfully screaming "Woo!" during action scenes like members of a fan screening.
Cut to The Last Jedi and one of the biggest lingering questions was about his childhood - or rather, how it was robbed from him by the First Order. We already knew he was "raised to fight" and that Jakku was his first battle (presumably from a life in sanitation meaning he never saw combat), but that's it.
As the cut material goes, in another version of Canto Bight, when Rose begins discussing her childhood as they watch the Fathiers race, Finn then shares his. The only detail we have for now is that Finn had other family members taken by the First Order, though that leaves wide open the notion that his family is not only still out there, but working somewhere within the enemy ranks.
This COULD be addressed in Episode IX, but with so many Episode VII plots being dropped - alongside even this small discussion also being axed - there's a chance Finn's backstory is already done.