Sirius Clinton Romanoff was born July 31, 2002. He was abducted by Hydra when they learn about Natasha's miracle baby.
Hydra made sure to make his identity was hidden and erased from any type of files so that SHIELD or his mother wasn't made knowledge of him. He will later be named as Stepan Dreykov. Dreykov's way of retaliation against Natasha. During his stay with Hydra he was experimented as an infant especially when his magic came out to play.
Later in his teens he meets the Maximoff siblings.
He will have the same abilities as Wanda but his powers will be in green version(Polaris tribute).
He will have a reunion with his parents but it won't be a happy hugs and tears of joy type of reunion.
Pairing : Sirius Romanoff x Penelope Parker
My fan cast will be Cody Christian and Kaylee Bryant. You can imagine them however you want.
All them will come from before Ultron happens.
I have no rights whatsoever to Marvel/Disney and Harry Potter universe.