User blog comment:Zathronas/Analysis by an author: Volume 2 episode 6: Burning the Candle/@comment-10380701-20140905013658/@comment-24218038-20140905021429

@soulslicer Cinder as Yang's mom has been debunked by Monty himself. Given how close they are of age, I never believed it anyway. Monty also debunked any relation between Blake and Cinder. I know the Yang and Cinder as sisters has been around for some time but every speculation was basically the same.

Either a ying-yang thing or a fire thing. That was flimsy at best. Now with episode 6 we have way more meat on this theory.