Back when 20th Century Fox and Disney were still separate entities, there was a few Marvel characters that both movie studios were able to use in their respective superhero franchises, albeit with some stipulations. This included Scarlet Witch and Quicksilver, although in Disney’s case, their versions of the characters could not be mutants since Fox owned the film rights to the X-Men. Of course, that’s no longer an issue since the Mouse House acquired Fox, and it seems like steps are now being taken to tie the MCU’s Scarlet Witch closer to the X-Men mythos.
Article source: https://www.cinemablend.com/news/2557462/wait-could-the-mcu-be-tying-scarlet-witch-closer-to-the-x-men