Hi Marc
I am a keen student of nobility myself and I am glad to share with you some information about illustrious Lieven family.
As alredy noted in this forum, the Lievens are believed to be descended from Livonian older or chieftain named Kaupo. It is known from sources that Gert Live was a vassal of Archbishop of Riga in 1269. A number of generations later family was divided into two main branches. Lüdeke Live´s two sons were founders of those separate lineages. Elder son´s name was Jürgen Live and his descendants went into Sweden eventually. They were given by the King of Sweden the title of freiherr (corresponds to Baron) in 1653 and Count in 1719. This branch is now extinct (Christian Vilhelm von Liewen who was the last male member of this family line died in 1917). Many Swedish generals sprang from this branch.
Another son of Lüdeke Live was Johann Live (died in 1501) who was founder of younger branch of the family. This branch split later in turn into minor branches (many of them are now extinct). The Russian Czars gave them the title of Count in 1799 and of Prince (Serene Highness) in 1826.
Joseph II, ruler of the Holy Roman Empire, made them Counts in 1789.
I hope that this information helps you. In future I want to put genealogical tables of Lieven family on display at my website
www.zone.ee/princeoftartu.