Background: Mystique (Raven Darkholme) is a fictional character appearing in American comic books published by Marvel Comics, commonly in association with the X-Men. Created by artist David Cockrum and writer Chris Claremont, she first appeared in the comic book Ms. Marvel #16, published in 1978. Mystique is a member of a subspecies of humanity known as mutants, who are born with superhuman abilities. Mystique is a shapeshifter who can mimic the appearance and voice of any person with exquisite precision, and her natural appearance includes blue skin and yellow eyes.
Context: Mystique becomes the adoptive mother of the four-year-old girl Rogue. Rogue had run away from her home in rural Caldecott County, Mississippi. The girl was living alone in a wooded area, brandishing a shotgun and trusting no one, when Mystique found her. Destiny foresees that Rogue will be important to them and Mystique seeks her out, gains her trust, and takes her in. She and Destiny raise the girl, and Mystique grows to be very protective of her.  Mystique, as Raven Darkholme, rises rapidly through the United States Civil Service to the trusted position of Deputy Director of the Defense Advanced Research Projects Agency (DARPA) in the United States Department of Defense. This position gives her access to military secrets and advanced weaponry, both of which she uses for her own criminal and subversive purposes. In this position, she attempts the theft of the Centurion weaponry from S.H.I.E.L.D. She also beat Ms. Marvel's lover Michael Barnett to death, and sought to kill Ms. Marvel.  To help her in her criminal activities, Mystique organizes her own incarnation of the Brotherhood of Evil Mutants, consisting of herself, Avalanche, the Blob, Destiny, and Pyro. The Brotherhood attempts to assassinate Senator Robert Kelly, a notoriously anti-mutant politician. The X-Men thwart the assassination attempt, and all of the Brotherhood save Mystique herself are incarcerated.  Rogue is trained by Mystique and eventually joins the Brotherhood of Evil Mutants. Her mutant power is the ability to absorb the memories, personality, and skills or powers of whomever she touches. To free the other members of the Brotherhood, Mystique concocts a plan involving Rogue absorbing the powers of Ms. Marvel and the Avengers. Though the plan is successful, the Avengers ultimately defeat the Brotherhood of Evil Mutants, capturing all of them except Rogue and Mystique. Moreover, Rogue finds that she has absorbed Ms. Marvel's memories, personality, and powers permanently. In a further humiliation, a confrontation at the Pentagon ends with Mystique being defeated and turned over to the authorities by a powerless Ms. Marvel.  The Brotherhood of Evil Mutants eventually escape, and battle against Dazzler. In an act of revenge against Mystique, Mastermind unbalances Rogue's psyche with the one she absorbed from Ms. Marvel, which prompts her to defect to the X-Men. Because Rogue left without a word, Mystique assumes that Professor X, the X-Men's mentor, brainwashed her. The Brotherhood of Evil Mutants accordingly launches an attempt to kill Professor X. Rogue stops Mystique, and explains that she joined the X-Men because Professor X, as the world's most powerful telepath, is her best hope of healing for her fragmented psyche. Mystique reluctantly relinquishes her guardianship of Rogue.
Question: What is Rogue's relationship to Mystique?. Whats the answer?
Mystique becomes the adoptive mother of the four-year-old girl Rogue.