Who is Eighth Count of Gretz from The Source; a Novel and what is their importance?

The eighth Count of Gretz resides at Ma Coeur in 1289. Volkmar, a descendant of the Family of Ur, is married and has an eleven year old son. He receives permission from the Mamelukes to make a pilgrimage around the area. He takes his son along and explains the history of what occurred at each site. On the trip he learns that there are rumors of a new Crusade beginning, but then hears it is not true.