Originally Posted by Mr. Dent
40 years?? It was retconned in 1982. It's not at all established in their background, I can't stress that enough. Magneto has absolutely nothing to do with the twins' backstory whatsoever beyond birthing them, which is not an essential or wanted element to their characters in the first place. He plays no role in who they become as adults, he plays no role in their classic tenure as Avengers, the era Joss read when he was a kid, and the retcon only served to take the characters in a different direction than what they were originally intended for because that storyline had run its course and was getting stagnant.
I disagree with that sentiment. Even before it was retconned that he was their father, he was still cast as something of a father-figure to them and their relationship with him was a pretty big deal for both characters.