HTML was spawned from SGML and HTML predates XML. The only XML ancestry was later on when a couple of versions of HTML were rewritten to be based on XML (XHTML

HTML was spawned from SGML and HTML predates XML. The only XML ancestry was later on when a couple of versions of HTML were rewritten to be based on XML (XHTML which was eventually abandoned), but even then it needed a lot of backwards compatible escape hatches, and was only valid XML with strict modes etc.