For Dylan O'Brien, Twinless meant confronting an emotion he's long dreaded. "Grief is, funny enough, something I have not experienced a ton," O'Brien, 34, exclusively tells Us Weekly. "I think about it in a grateful way and in a fearful way, in that I fear I won't be able to handle it." Yet the 34-year-old found himself drawn to this script about, as he calls it, a very "unique type of loss.