As you may already know, some characters existed within a legal grey area and were fair game for both Disney and Fox. Chief among them were Quicksilver and the Scarlet Witch, the former of which wound up having two live action versions of him existing at the same time. The alien race known as the Skrulls were also of this ilk, though they wound up being called something else in Dark Phoenix.
Nick Fury, however, wasn’t residing over at Fox, though they did try to get him at one point. Believe it or not, Andre Braugher’s character in Fantastic