In Avengers: Age of Ultron, is the Maximoff twins’ father Magneto?
Because in the comics he is, but in the movie they said the Maximoff twins’ parents died, and Magneto would not really die that easily, so is he their father?
I don't believe there are enough facts about their father to say definitively Yes or No.
The only facts known at this point are
Whether it's relevant is another matter entirely since they presumably they cannot use him in any meaningful way, hence why killing him off was an easy option.
My answer is based off of this answer, which I think makes this question a duplicate:
This means that neither cinematic universe is necessarily beholden to Quicksilver's comic past of being Magneto's son
an agreement exists that allows Marvel to use them provided that no reference is made to their traditional origins
From an interview with Kevin Feige
Feige: We both have them. There’s a specific arrangement ... not [to] discuss or reference their mutant or Magneto-related lineage. ”
Emphasis mine. Note that last part. That precludes any MCU version of Magneto existing mutant or otherwise.
That only conclusion is that the MCU twins have some other non-magneto-related lineage.