Raven, Mike and Hope: They helped the Bartons.
Mike: He jumped in.
Hope: She waded in, more cautious.
Raven: She sat on the dock.
OOC: Very cool, thanks.
They're twins, half German half Scandinavian if I remember correctly. They're mutants. Pietro Maximoff AKA Quick Silver has super speed, and Wanda Maximoff AKA Scarlet Witch can manipulate luck to put the odds in her favor, has these "hex bolts" and can do some illusion type things.
I don't know how the Marvel Cinematic Universe (MCU) will change things, but here, in a nutshell, is the original story as I understand it:
Story goes they were orphans, and when they were being hunted for their mutations Magneto saved their lives and so they joined the Brotherhood for a time. Then they learned/figured out that they were actually the children of Magneto (they use their mother's last name rather than their father's) and shortly after that they kind of realized that what they were doing in the Brotherhood was wrong, so they decided to become good guys. But they had fought the X-Men a lot and didn't think they would be welcome and kind of wanted the focus to be on them being Wanda and Pietro, not them being mutants, so they joined the Avengers.