There is a story called "Your Wizarding Twin" by mortal_star . It is a story mixed with 'Gravity Falls', and 'Fantastic Beats and Where to Find Them'.

If you like those two things, that story is for you! It has under 100 views, and I honestly think it should have more. It's so well written, and just so awesome! Currently, there are only two chapters, though both chapters are pretty long.

So go and read it!

~Griffin