The Tsar of Russia, Peter the Great, received a promise from Friedrich Wilhelm that he would marry one of the daughters of the tsar's brother.
Prince Ernst-Johann Karl Oskar Eitel-Friedrich Peter Burchard Biron of Courland (born August 6, 1940) is the senior male-line descendant of Ernst Johann von Biron and as such heir to the Duchy of Courland and Semigallia.
Peter von Biron, last Duke of Courland and Semigallia died at Jeleniów Palace on January 13, 1800.
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