Wanda and Pietro’s characters are first introduced to the audience in the post-credit scene of Captain America: The Winter Soldier. HYDRA experiments on them and gives them both superpowers. They seek revenge on Tony Stark because they hail from Sokovia. They realise they are on the wrong side when they find out Ultron’s intentions and join the Avengers.
Scarlet Witch of the MCU will be the main lead of WandaVision by Disney+. There is also major speculation that Quicksilver will return in this series. Scarlet Witch, aka Wanda Maximoff loses her twin, Pietro, when he dies trying to do a greater good during their first fight alongside the Avengers. As the show clearly shows that Vision is back from the dead, mostly because of Wanda’s powers, it is safe to assume that she also brings back Pietro.
Quicksilvers characters did not appear in the MCU since his introduction in 2015’s Avengers: Age of Ultron. Which is unusual because of the character being very important in the comics. One of the more accepted reasons why his character was not returned to the MCU was because of the character in X-Men movies by Fox.
A few rumors have reported that Pietro’s character will return in Doctor Strange as Scarlet Witch has a prominent role in the sequel, although now, it seems more likely that quicksilver will return sooner in WandaVision. There are a few sources that are still uncertain about in which of these two MCU directions, quicksilver will feature. It is either in WandaVision or in Doctor Strange 2, but the fans will most definitely get at least a glimpse of Pietro.
Scarlet Witch is said to become the most powerful character of the MCU.
In any case, seeing Wanda and Pietro together as a family will be a dream come true for all the fans. Moreover, WandaVision showing a family life between Vision and Wanda and their rumored children is what every Marvel fan has dreamt of as most of the love stories of MCU have very tragic endings and mostly never live their full course. Waiting for a family spin-off of the MCU characters is finally coming to an end.