Joss Whedon recently announced that he would include a brother-sister act in The Avengers 2, which was later revealed to be the popular characters of Quicksilver and Scarlet Witch. Specifically, popular X-Men characters. You see the rights issues surrounding studio ownership of Marvel's vast and diverse cast of characters is extremely complicated. Whilst it's truth that 20th Century Fox own X-Men and Fantastic Four characters and Sony Pictures own the rights to Spider-Man, Marvel Studios are technically available to use certain characters as long as they aren't called mutants. The line on what characters are eligible for this is apparently determined by if, and how long, the characters have enjoyed shelf time as part of The Avengers comic series. This is how Whedon got Quicksilver and Scarlett Witch, and he'll need to be careful with his sequel not to break any copyright laws and call them mutants. Of course not to be outdone by Whedon, rival studio director Bryan Singer confirmed that he was also planning on using Quicksilver in his already shooting X-Men: Days Of Future Past. One half of casting came quickly... American Horror Story actor Evan Peters will play Quicksilver, however Scarlet Witch has yet to be cast. For Marvel, Kick-Ass actor Aaron Taylor-Johnson is in talks to play the silver speedster in The Avengers 2. So what we are left with is two upcoming movies that are set to introduce to us the exact same characters on the big screen for the first time... a particularly confusing moment as comic book audiences are now trained to be aware of cross-continuity between superhero films, especially those involving Marvel characters. Here's four reasons why there really should just be one Quicksilver and Scarlet Witch on our screens;