I am a descendant of the von Ungern-Sternberg family, and am researching them. They are a very old family (about 700 years), and have strong roots in Estonia. Many historic buildings in Estonia were built by this family including Schloss Linden also known as Ungru Manor in Kiltsi near Haapsalu.
If you are interested in the history of the von Ungern-Sternberg Family, there is an edition from the 19th Century, which you can get in reprint from the publisher Harro von Hirschheydt.
Write to: Kontakt@Hirschheydt-online.de
You can see a little bit more in: www.Hirschheydt-online.de
if you look for 'Rudolf Frhr. von Ungern-Sternberg, Nachrichten über das Geschlecht Ungern-Sternberg'.