SPOILER ALERT If you have not scene Captain America The Winter Solider read no further, unless you don't care.
If you for some reason you didn't stay for the post credits clip in the [Captain America: The Winter Soldier](movie:254973) then I inform you that [Quicksilver and Scarlet Witch](movie:1081109) make an appearance in the post credit scenes.
So now that we've established that Quicksilver and his twin appear, lets discus who introduced them Baron Von Strucker.
Strucker is 2nd in command of HYDRA next to Red Skull. (Who hasn't made an appearance since the First Avenger) In the scene Von Strucker is explaining what HYDRA's next move is, and as he addresses the "Twins". Also the Twins seemed to be just then developing their abilities as thought HYDRA made them what they were. So now we know that they're not mutants, but rather Super solider's.
- Given the set photos that reveal Hawkeye fighting next to Scarlet Witch rather than against her it appears that they the twins were not willing candidates to HYDRA's science project. Only time will tell what side they're on in the upcoming movie.