​If you’ve been tuned into the Spider-Man: Brand New Day rumor mill, you might not be too surprised by one of the big reveals in the film. Sorry to be so vague, but we're honor-bound to protect our readers from Spider-Man: Brand New Day spoilers. Warning: Spoilers ahead for Spider-Man: Brand New DayWho is Jean Grey's sister Sara Grey in Spider-Man: Brand New Day? When she returned, Sara had the mutant ability to sense mutant powers in others and unlock them. Spider-Man: Brand New Day is now in theaters.