Wanda Maximoff

Scarlet Witch is Quicksilver's sister.

Captain America: The Winter Soldier
Wolfgang von Strucker led a HYDRA agent to "the twins", and declared it was the "age of miracles". Quicksilver and Scarlet Witch were held in separate cells, imprisoned in the HYDRA headquarters.

Avengers: Age of Ultron
To be added

Relationships

 * Quicksilver - brother
 * Baron Von Strucker - Ally turned enemy
 * Ultron - Ally turned enemy
 * The Vision - Ally
 * The Avengers - Enemies turned ally

Appearances/Actresses

 * Marvel Cinematic Universe (2 films)
 * Captain America: The Winter Soldier (First appearance) - Elizabeth Olsen
 * Avengers: Age of Ultron - Elizabeth Olsen

Behind the scenes
To be added

Trivia

 * Elizabeth Olsen took the role after Saoirse Ronan passed on the offer.
 * Elizabeth Olsen's role in Captain America: The Winter Soldier was uncredited.