This is based on the fact that if you die while polyjuiced changed as someone else, you don't change back.
What if it wasn't Fred...
What if he was- is- still alive...
What if he found his twin...
Living as a twin is hard, living as the noticed, unloved twin of the BWL is harder. Ember had long ago given up telling people what really happened that night, now she focuses on herself. WBWL, Fem Harry, Alive Potters, Dumbledore bashing, bashing galore.