I get a lot of ideas from asking myself ‘what-if’ questions, from thinking about ways to subvert or re-do tropes (I’m currently messing with the Chosen One trope), and from history. Seriously, I can’t read my history textbook without getting a ton of ideas about characters and plotlines. I also get inspired by things from my life–usually an interesting person I’d want to turn into a character or something funny I heard someone say (little kids are great for this).
One thing I’d suggest is making a list of things you absolutely love in stories and seeing if you can brainstorm something from that. Beverly Cleary said write the book you want to read. I don’t think you should waste time with a story you don’t like. (Now you may not like it every day you’re writing it, but you get my idea, yes?)
Another idea–think of a book or story you disliked and think of how you would have changed it to make it better. I still need to do this with A Wrinkle in Time.
And you can always try to make your shorter ideas into short stories!
(Also, I’ve seen you post about your WIP and lemme just say, it sounds awesome! I didn’t even know Paul had a sister.)
Hope this helps!
"For He knows our frame; He remembers that we are dust." - Psalm 103:14