Board Thread:Questions and Answers/@comment-35718513-20191020022158/@comment-5398287-20191020023632

Yhwach had been alive for over 200 years by the time he encountered Bazz-B and Haschwalth, and that event took place over 1000 years before the present day, as he then fought Yamamoto for the first time and was defeated. That's not an inconsistency. We don't know why Bazz-B and Haschwalth are still youthful - that may have been something Kubo was planning to address before the manga was rushed to its end.