George III named his fifth son Duke of Cumberland and Teviotdale while Queen Victoria created her fourth son, Leopold, Duke of Albany.
In 1837 the Duke of Cumberland succeeded his brother William IV as King George V of Hannover (Victoria couldn't inherit Hannover due to its refusal to allow female inheritance).
In 1900 following the death of Queen Victoria's second son, Alfred, her grandson - Leopold's son, Charles inherited the title of Duke of Saxe-Coburg Gotha from Alfred.
As a result in 1914 the holders of both these titles found themselves as British princes and the holders of British peerages but as Germans committed to a German cause.
As WWI unfolded the idea of British citizens, who were also peers of the realms and thus able to sit in the House of Lords and vote on decisions (they didn't do so but they had that right) became a cause of tension so the King and Parliament passed the Titles Deprivation Act which basically said that the then holders were no longer entitled to use those peerages or have any of the benefits of those peerages. The Act, however, did say that future heirs could appeal to have the titles reinstated.
As a result none of Cumberland, Teviotdale or Albany are available as there are current heirs of those deprived nearly 100 years ago and the law is clear - while there are heirs male of the body the titles still exist and aren't able to be regranted until there are no male line heirs which will some generations now as their are multiple generations of heir e.g. Ernest of Hanover has two sons, one of whom only recently married.
The aforementioned Charles - Duke of Albany - who was deprived of his title is sometimes called Hitler's royal as he did embrace the Nazi cause as well as an older man. He had been a teenager whose father died before he was born when he had moved to Germany to take over Saxe Coburg Gotha when Alfred died leaving no sons to inherit.
I wouldn't make the connection to Beaulieu ?
