I am a fan of the Scarlet Witch (Wanda Maximoff) and Quicksilver (Pietro Maximoff) being the children of Magneto.
I grew up knowing that they were part of the Brotherhood of Evil Mutants before joining the Avengers.
In my opinion this made them both unique as they were part of the main superhero team yet their father was one of the main super villians of the Marvel Universe.
After their background retcon in Uncanny Avengers# 4 vol 2 I was very disapointed.
Sure Fox Studios owned the movie rights to the X-Men but I believe Marvel went down the wrong road by changing the Maximoff twins history and also trying to have the Inhumans replace the X-Men.
Hopefully now with the Disney/Fox sale all but complete Marvel will right this wrong to Marvel continuity.