When you're an adolescent, you suddenly wake up one morning and your body is an enemy. There are hormonal changes, physical changes, emotional changes. People are saying to you, 'Now you have to make the decisions that define the rest of your life.' The X-Men takes those elements and pushes them one giant step farther.
In terms of the 'X-Men: Days of Future Past' movie, Bryan Singer has been a part of the X-Men family from the first movie. He knows about the comics canon and how it relates to his work as a filmmaker. He's more well versed in the canon than most, as are the people that are working with him.