That's right, X-Men fans, Charles Xavier once married Mystique. The movies have established a close relationship between Charles Xavier and the shape-shifting Mystique. In fact, according to X-Men: First Class the two basically grew up together. In the comics, however, the two have seldom crossed paths - and they've usually been fighting for very different causes.
Charles Xavier is typically portrayed as dreaming of peaceful coexistence between man and mutant, while Mystique is willing to take direct action to remove the people she perceives as threats. For all that's the case, though, during his X-Men run writer Brian Bendis revealed Charles Xavier and Mystique are rather more intimately connected than the X-Men had realized.
Xavier had been killed at the climax of 2012's "Avengers Vs. X-Men" event, and in Uncanny X-Men #24, Xavier's students assembled for the reading of his will. This was being presented by She-Hulk, and it was a deeply unpleasant moment for everyone present, not least because the X-Men were in the midst of a sort of mutant schism at the time. Still, Cyclops and Beast managed to sit down in the same room, only glaring at one another every now and again. And then She-Hulk began reading the will, shocking them from the outset.
"I, Charles Francis Xavier, of the town of Salem Center, County of Westchester, and State of New York, being of sound mind and memory, do hereby make, publish and declare this to be my last will and testament, hereby revoking all wills and codicils previously made by me. I declare that I am married as of the date of this will and that my wife's name is Raven Darkholme."
Naturally, the X-Men were more than a little taken aback, not least because at the time Mystique had once again become one of their most dangerous recurring foes. In fact, she'd kidnapped and replaced Dazzler for months, subjecting her to torture in order to extract Mutant Growth Hormone from her DNA; Dazzler had only recently escaped, and had sworn to kill Mystique with her bare hands. Storm guessed this was why Mystique had fallen so far off the rails of late - a demonstration of her grief over Xavier's death.
The idea is a surreal one, and more than a little entertaining; the X-Men themselves were left reeling, especially Wolverine and Iceman, both of whom had slept with Mystique in the past. Cyclops and Storm briefly faced the possibility Xavier had left the school to Mystique, with Cyclops resolving to kill her before she ever got the chance to step foot on the grounds. Meanwhile, X-Men fans were left scrabbling through back issues, desperate to figure out how this fitted into continuity.
By the end of the arc, though, they'd realized it didn't matter how it fitted at all. Xavier's will revealed another secret, an incredibly powerful mutant whose existence he had hidden for decades. By the end of the arc, one of the X-Men was forced to use time travel to erase this mutant from history; the course of Xavier's own life was subtly changed as well, and as an unexpected side affect his marriage to Mystique was erased altogether. Moving forward to the present, the resurrected Xavier and Mystique now both live on the mutant nation of Krakoa - and they're secretly at odds once again, with Mystique intending to burn it all down.