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The two have been cast as super-powered twins the Scarlet Witch and Quicksilver, and it will definitely be interesting to see how they'll play up the comic-based film. In the Marvel comics, the Scarlet Witch and Quicksilver are children of Magneto, the metal-controlling mutant from X-Men. 

The "Avengers" sequel will be the first major motion picture for Olsen, who's known for her dramatic role in "Martha Marcy May Marlene" and other independent films. Following the acting footsteps of her twin sisters, Olsen has definitely become an It Girl of the generation.

Taylor-Johnson is mainly known for playing Kick-Ass in "Kick-Ass" and its sequel, where people can identify him with similar comic-related superhero roles. Of course his role in "Avengers: Age of Ultron" will be much more action-packed than comedic.

Though the pair will be playing siblings in the "Avengers: Age of Ultron," they will also be playing a married couple in the remake of "Godzilla," set to be released in May 2014.

"Avengers: Age of Ultron" is expected to hit theaters May 1, 2015.

Contact Staff Reporter Dale Chong here. Follow her on Twitter here.