Who Owns Who
Sony Picture owns the rights to Spider-Man and any character directly related to his story.
Marvel Studios own the rights to every character that has not been sold to a different sudio. Marvel Studios & 20th Centuey Fox share the rights to Quick Silver & Scarlett Witch, but do to the fact that 20th Centuey Fox owns the rights to the term "Mutaints" & the X-Men Characters Quick Silver & Scarlett Witch cannot be refered as Mutaints or have any relation to Magneto
Scarlet Witch & Quicksilver
Please Note that Scarlet Witch DID NOT appear in "Days of Future Past". The little girl bieng held by Quicksilver/Pietro Maximoff is his younger sister.
Here you Can find all of the Characters that appeared on other movies.
Marvel Cinematic Universe.
Source: Reddit User OhJayPea
Box Office Nunbers
Marvel Cinematic Universe