They first met an X-Man while on safari in Africa, where Storm was at the time, her powers were removed accidently by the gun designed by Forge. There, she vanquished them both to protect the natives, being recognized again as a goddess. However, the twins vowed revenge and had their chance during the trial of Magneto in Paris. Magneto was one of their targets as well, for he had helped Xavier to defeat their father and had stolen gold Von Strucker was using to finance HYDRA to promote his own projects. Of course, they didn't succeed, but kept trying until they joined the Upstarts, killing mutants to gain points in the game where the prize was, presumably, immortality.

Fenris is actually a criminal organization, consisting of your basic small army of men in battlesuits with big guns, led by the Strucker's.

Most recently, the brats showed up in Generation X '96 where they ran into some of the members of Generation X. While trying to succeed in another terrorist act that involved a machine which basically makes mutants go ballistic and causes their powers to go out of control. They thought Banshee and the kids were there to stop them when they were really just passing by in the city. But the did stop them, eventually. Letting it be known that these two brats still suck at terrorism.