(laugh all you want, i know this is very spergy...)

Both pair of siblings have a sister with powerful but uncontrollable magical abilities that stress her out big time when she can't control them, and the other part of the pair is a sibling who may be a bit foolish by jumping into dangerous situations without thinking of the consequences but they are dedicated and loyal to their sister and would die for them. They're also orphans, have had bad romantic relationships with the first person they fell in love with, and both pairs have a sibling that has silver-white hair and wears bluish clothing.

I haven't seen The Avengers, so I wouldn't know...

should be a "haven't seen yet" option because I cant really judge.

^Me too.

I wouldn't say "You're bonkers" because people see things differently and that's fine, but aside from the fact that they're two pairs of siblings who deeply care for each other, I see no similarities.

I agree ^^

I see a few similarities, but Elsa and Anna are nowhere near as awesome as Pietro and Wanda.

Edited it for those of you who haven't seen the movie.