I noticed several people worried that Quicksilver and Scarlet Witch couldn't be mutants in Avengers 2, first off neither Fox nor Marvel own the word Mutant, it is technically a biological term and has been used in various sci-fi stories since before the X-men were created so there is a good chance they can still be mutants. Even if by some legal wrangling Fox figured out a way to prevent them from being referred to as mutants there are many ways around this.
For instance the term mutation is up for grabs so they could explain that they were given their powers through genetic mutation and be done with it. As for the Magneto thing, it is very easy to deal with that. Don't bring him up, there are many people with far better relationships with their parents than they do with Magneto who rarely ever bring up their parents in conversation unless a holiday is coming up or they happen to get a call from their parents.
Given their relationship with Magneto its entirely possible that they wouldn't even want him brought up. They could honestly fix the issue with a line, just call him a terrorist and have one of them say they don't want to talk about him.
Not saying I like the idea of not bringing up Magneto at all just saying its entirely within the realm of possibility that they just wouldn't bring their parents up.