The reigning Grand Dukes (and Grand Duchesses) of Luxembourg come from the same Nassau Family as the Monarchs of The Netherlands, although technically from a different line. Luxembourg has been a grand duchy since 15 March 1815 when it was created from territory of the former Duchy of Luxembourg. It was in personal union with the United Kingdom of the Netherlands until 1890 under the House of Orange-Nassau. When William III of The Netherlands died leaving only his daughter Wilhelmina as an heir, the Crown of the Netherlands, not being bound by the family pact, passed to her. However, the Crown of Luxembourg passed to a male of another branch of the House of Nassau: Adolphe, the dispossessed Duke of Nassau and head of the branch of Nassau-Weilburg.
In 1907, Adolphe's only son, William IV, obtained passage of a law confirming the right of his eldest daughter, Marie-Adélaïde, to succeed to the Throne to prevent a succession crisis due to his lack of a son, as the Nassau Family Pact stipulated Salic Law or male-only succession. She became the Grand Duchy's first reigning female monarch upon her father's death in 1912 and, upon her own abdication in 1919, was succeeded by her younger sister Charlotte,
As we saw in the previous blog about The Netherlands, there are two branches of the family of the Counts of Nassau, which resulted from two brothers, Count Walram II and Count Otto I, agreeing to divide their father's (Henry II) lands between them in 1255. The Monarchs of The Netherlands are descendants of count Otto. The Grand Dukes of Luxembourg are descendants of count Walram.
As can be seen above, the Royal Crest of Luxembourg is nowadays the Royal Crown. The second illustration shows Adolphe's Greater Coat of Arms which shows a number of Quarters and Crests from the number of counties and titles he held. These include the Walram Crest in the centre:
"Between two trunks Azure billetty Or a sitting lion Or."
Over time, the Coat of Arms of the Grand Dukes of Luxembourg has been simplified all over, Shield and Crest(s). Technically, if Crests were used by the Luxembourg Royal Family as they are in the Dutch Royal Family, they would have to include Bourbon Parma as in the Inescutcheon (a word I haven't used for too long a while...) on the shield. Grand Duke Henri's Grandfather was Prince Felix of Bourbon-Parma, married to reigning Grand Duchess Charlotte. As the House of Bourbon Parma is a cadet branch of both the Spanish and French royal families, it is doubtful if a Crest exists.