Snadinator
Super Freak
I don't see how either of them could be in both. Fox has the rights to the X-MEN movie franchise and I'm fairly sure that Marvel doesn't want to give away any more of their characters rights to them. Marvel can't make any X-MEN or Spider-man movies because Fox and Sony have the rights to those characters. Marvel/Paramount have the Avengers and Avengers related characters as well as any characters they haven't licensed off to other studios. This is actually kind of a mess for Marvel until they can get back all of their movie characters and put them under one movie studio.
It has already been confirmed that Quicksilver is in both films. Not the same actor or even the same era. Fox can use him with their X-Men contract and Disney can use him for Avengers.