With Wanda and Pietro in the current The Avengers 2 script, it's likely that they will appear in the movie. Here are my ideas for actors and actresses to play the sibling duo. I know some of them are a little young compared to the rest of the cast, but somehow I could see that working in the movie. (Note: the actors are paired together based on who I think would be believable as brother and sister.)
ALEXANDER SKARSGARD & EVA GREEN
SHILOH FERNANDEZ & PHOEBE TONKIN
MICHAEL ROSENBAUM & OLIVIA WILDE
NICHOLAS HOULT & KRYSTEN RITTER
Comment with your own ideas! ... Or just tell me how stupid I am for considering these actors!