User blog comment:Dangai Train/Yhwach's backstory/@comment-5695542-20131011054804/@comment-11051098-20131013014823

What I mean is, if they really should be related, it would be strange because one is implied to be a powerful living human, while the other one was a powerful soul, a deceased human. In other words, one is implied to be a living human while the other was the soul of a dead human for his entire lifetime of 2100+ years.

If Yhwach should turn out to be a soul with Quincy-powers, like Yamamoto was a soul with Shinigami-powers, then it could be possible.