His Ancestors Were German Kings. He Wants Their Treasures Back.

“It is not just about family history, it is German history,” he added.

Prinz von Preussen’s great-great-grandfather, Kaiser Wilhelm II, was the last emperor of Germany and by far the richest man in the country before World War I. After Wilhelm abdicated in 1918, he retained substantial wealth: At least 60 railway wagons carried furniture, art, porcelain and silver from Germany to his new home in exile in the Netherlands. The kaiser and his family also held onto substantial cash reserves and dozens of palaces, villas and other properties.

But after World War II, the Hohenzollerns’ forests, farms, factories and palaces in East Germany were expropriated in Communist land reforms, and thousands of artworks and historical objects were subsumed into the collections of state-owned museums.

Prinz von Preussen’s claim for restitution was first lodged by his grandfather after the fall of the Berlin Wall, when thousands of Germans took advantage of new laws allowing them to seek compensation and restitution for confiscated property. Officials assessed it for more than 20 years before negotiations with the family began.

If Prinz von Preussen pursues the case in court, success could hinge on how much support his great-grandfather, Crown Prince Wilhelm, gave to the Nazis in the 1930s. Under German law, if a court deems someone lent the Nazis “substantial support,” then their family is not eligible for compensation or restitution of lost property.

The crown prince hoped that Adolf Hitler would reinstate the monarchy, and wrote him flattering letters. He defended Hitler’s anti-Semitic policies and wore a swastika armband in public. If a court were to agree that Crown Prince Wilhelm’s support for Hitler was “substantial,” then Prinz von Preussen’s claims would be dismissed.

Prinz von Preussen said his great-grandfather had “recognized this criminal regime, and it very quickly became clear that he didn’t have the moral fortitude, or courage, to go into opposition.” But he questioned whether that amounts to “substantial” support, adding that this was a “question that has to be cleared up by legal experts.”