I just thought of an interesting backstory for Null. Mister Sinister, in an attempt to make the perfect mutant, created him. however, he left him in the care of who he deemed best with the intent of his power awakening at a point. the 1 thing he didn't foresee was the Shadow King learning about Null and when Null's power awoke, Xavier took the chance to bring him to the mansion and try to guide him down a better path than what he was originally supposed to be. the team could even write how Null wasn't super close to his "family" and they treated him with indifference other than playing the part of loving parents in a public setting