He was born and spent much of his childhood in Monaco, where his mother Florestine often managed the government during the extended oceanographic expeditions of her nephew, Prince Albert I. Wilhelm was culturally francophone.

[2] After the accession of Prince Louis II in 1922, Wilhelm renounced his rights of succession to the throne of Monaco in favour of distant French cousins, the counts de Chabrillan, in 1924.

From June to September 1915, the division moved from north of Warsaw to positions close to the Neman River, an advance of hundreds of miles in the campaign in which Poland was taken (the Great Russian Retreat of World War I).

The division served at Ypres in Belgium from December 1915 to July 1916, then was largely destroyed at the Somme battles from August to November 1916 while holding the Schwaben Redoubt (Swabia is part of Württemberg).

The German government did not recognize Wilhelm's selection as king, although the influential publicist and politician Matthias Erzberger, also a Catholic from Württemberg, supported the claim.

In the tiny chapel of Lichtenstein Castle is a framed letter from Pope Benedict XV welcoming Wilhelm's selection as the future king of Lithuania.

[15] In 2009, Wilhelm's grandson Inigo was interviewed on television in Vilnius, and said: "...if he was honoured with a proposal to assume the throne of Lithuania, he would not refuse it.

"[16] The German anti-war novelist Arnold Zweig set his 1937 novel Einsetzung eines Königs (The Crowning of a King) around the election of Mindaugas in 1918.

Prince Eberhard's son Inigo made a sentimental journey to Lithuania in November 2009, which was covered by the local media.