Mark Seibert can refer to two different people: An American musician, composer and producer best known for his work on various video games from Sierra Entertainment, such as Quest for Glory/Hero's Quest, King's Quest IV and V, Space Quest III, Conquests of Camelot, and Phantasmagoria. http://www.markseibert.com/ Or Mark Seibert (* 9. April 1979 in Frankfurt am Main) ist Musicaldarsteller. 2005/2006 war er in der Rolle des „Tybalt“ in „Romeo & Julia“ im Wiener Raimund Theater zu sehen.