X-Men start out as members of a kids show (think Power Rangers).
Scott Summers - 17
Jean Grey - 16
Hank McCoy - 18
Warren Worthington - 17
Robert Drake - 14
Xavier creates the X-Men TV show to get young people comfortable with the idea of mutants believing that soon the truth would get out.
Mutant age slower than humans. Two-to-one for the average mutant. Longer for more powerful mutants.
There are only a few thousand mutants world-wide. All mutants hid their powers out of fear.
Mutant sightings are like Bigfoot sightings, but quietly governments of the world take the idea more seriously.
Xavier and Magneto were members of a secret society of mutants (The Hellfire Club). The Club has been in existence for hundreds of years, with the mask of being a reputable social club for the very wealthy. Xavier quits after realizing that they are using their abilities for wealth and power. Magneto stays on longer only to be ousted for petitioning for mutants to come out of the shadows to conquer humanity.
The Hellfire Club had been actively covering up the existence of the mutant gene, but when a Scottish geneticist discovers that MI-6 had a mutant operative, the secret gets out on the internet (ala Wiki-leaks). The public becomes panicked and fearful. The backlash is immediate and it turns neighbor against neighbor with a new word being used..."mutie".
To make the best of the situation the Club organizes the murder of two young mutant children and blamed it on anti-mutant radicals. These deaths enrage Magneto into action. Magneto appears before an anti-mutant rally and begins tear down nearby buildings, flinging cars, and threatening to kill them all. An unexpected group appears to stop him, teen heartthrobs and actors, the X-Men.
For a moment, the police and National Guard begin to turn their weapons on the X-Men when some children in the crowd begins to cheer. The X-Men attack, but are hopelessly outmatched until Jean senses a hair-line fracture in Magneto's psionically shielded helmet and with the help of Xavier they are able to get Magneto to drop his shields. That is all the team needs to press the advantage and defeat Magneto.
In a secret prison, it is revealed that it was the Hellfire Club that order the murders and the anti-mutant rallies, all to manipulate Magneto into becoming the face of the "evil mutant" to the public. Unknown to Magneto, it was also the Club that tampered with his helmet allowing the X-Men to defeat him.