I find the twins treating Magneto like a father just jarring and out of character. They learned to grudgingly accept him at all because of their blood ties. That was what held them together tenuously. Without that blood tie, I can't believe the bond would hold. Their prior history was just too ugly to make me believe they had family feelings.
It was a terrible storytelling decision based on movie rights, not organic storytelling, and they all lost something in the potential of their characters and connections.