There were so many things that Remus wanted -- and was being asked -- to believe in right now. That he could change the future, that he'd go back in time to do it, that James would be here and even if they couldn't go back then yes, that they would at least all be together here, in this crazy version of New York.
He tired of thinking of these things -- of what happened, of what could have happened, of Peter who was still his friend, a friend who never betrayed his lycanthropy to anyone -- and remained stubborn that he needed more time to contemplate they're possibility. So looking at their hands together, he simply nodded to it. "Yeah," he croaked, trying to be a little more positive for Lily who was trying to be his ray of sunshine, "yeah, I know..."