Comic book fans will be well aware that Magneto is Quicksilver's father, and helpfully, this is subtly hinted at in Days of Future Past, albeit in a non-intrusive way should they not want to directly deal with it in any future X-Men movies. When speaking with Magneto, Quicksilver tells him that his mother used to hang around with a man who could control metal, and while obviously a) there could theoretically be another mutant who could control metal and b) that's not proof that they conceived Quicksilver, it's still a line that would seem completely throwaway if it isn't slyly implying this to be the case. It's not a huge moment of the movie by any means, but for those aware of what it suggests, it provides a decent chuckle.