Re: Magneto and the Brotherhood? (Spoilers)
My Brotherhood line-up:
The arc I can think of for the Brotherhood: they awaken Apocalypse to enslave humans and make the mutants rule. Apocalypse turns Magneto's four teammates including his 2 children into his Horsemen, Magneto barely escapes, goes to Xavier and asks for his X-Men' help to free his 2 children along with Toad and Sabretooth. Something like that.