Originally Posted by cherokeesam
Wanda & Pietro had that backstory for decades before somebody thought it'd be neato to make Mags their deadbeat dad.
Magneto tried to kill Quicksilver and Scarlet Witch several times in the mid-60s. They clearly weren't created as his children, it was just an idea 15 years later that worked.
In addition to the Maximoffs, there have been times and timelines where they had other parentage. In Heroes Reborn, The Enchantress was their mother. Prior to the Magneto reveal, it was thought that The Whizzer was their father. I don't particularly like either take, but the fact is, Magneto was kind of a shock value reveal, not something that has been part of their characters since day one.