10. Stan's Siblings Theory 2
This chapter by Prez Cipher
Okay, I bring you a highly improbably theory. With a story!
Just hear me out on this; maybe Stan's twin... is Bill!
Okay, so Stan and Stanley researched the mysteries and creatures in the journals together. Eventually, they got into a disagreement, and Stanley summoned Bill. Before they could make the deal, however, Stan lunged for Stanley and Bill in the blue light of the flames. Instead of stopping the deal, it combined Stanley and Bill. Bill still holds the grudge, hence why he doesn't like Stan much. The reason Stan wanted to combine the journals for the portal was he wants to save his twin from Bill!
... I know, it doesn't make much sense.