DW : Central Europe's Aristocrats Want Ancestral Fortunes Back

Quote Originally Posted by Deutsche Welle
Central European nobility struggling to regain palaces and property seized by the communists after World War II face an uphill battle. For many, the campaign ends in defeat.

Despite some notable successes, including the recent return of a Romanian fortress known as Dracula's castle to a descendant of the Habsburg dynasty that once ruled Austria-Hungary, aristocrats often see their ambitions to get ancestral property back thwarted by lengthy legal wrangling, vested interests or hostile public opinion.
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In early July, Duke Albert Czetwertynski, his family and dozens of supporters staged an angry demonstration in front of the United States embassy in Warsaw, demanding the return of a site they claim was stolen from them.
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According to Szypowski, less than 40 percent of the Polish public are in favor of re-privatizing nationalized property, down from 60 to 75 percent in the early 1990s.
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In neighboring Bulgaria, former monarch Simeon Saxe-Coburg, who fled his homeland as a child in 1946 after communists took over and who returned from exile five years ago to become prime minister from 2001 to 2005, now lives in Vrania Palace in Sofia.

He is a beneficiary of a decision by the constitutional court in 1998, allowing restitution of nationalized royal property
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But Czech claimants also face complications. Cases involving aristocrats are often tangled up with controversial decrees passed in 1946 under which some three million ethnic Germans were expelled from Czechoslovakia and had their property seized.
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Very informative article. I suggest that you read the full version.

In Western European countries (esp. monarchies) where the French Revolution abolished nobility (e.g. Benelux...), it is apparently possible for some individuals or families to reclaim their nobility title by proving that they are the direct descendents (often in primogeniture) from the person from whom they claim the surname and title. There has been severaal such case, for instance the Breydel family, who managed to prove their lineage from14th-century Flemish hero Jan Breydel, and obtained a nobility title from the King of Belgium.