John III of Dreux (in French Jean III de Dreux) (March 8, 1286 - April 30, 1341), known as the Good, was duke of Brittany, from 1312 to his death. He was son of Duke Arthur II and Mary of Limoges, his first wife.
John married three times but died with no male heirs. He married firstly, in 1298, Isabelle, sister of Philip IV of France; secondly, in 1310, Isabella, daughter of Sancho IV of Castile; and thirdly, in 1329, Joan, only child of Edward of Savoy. His death triggered the Breton War of Succession (1341-1364), which opposed the House of Blois and the rights of his niece Joanna of Dreux, to the House of Monfort, a cadet branch of the ducal family of Brittany, lead by John of Montfort and his homonymous son. This civil war was an incident of the Hundred Years War.
The Duke of Orléans was unpopular with the people and was held responsible for the disorders and the taxations under which the kingdom groaned, during the madness of the king, his brother.
The Duke of Burgundy, on the contrary, was very popular; he was regarded as a friend of the commoners and an opponent of taxation and abuses, while the university was grateful to him for his lack of sympathy with the Avignon pope.
The Duke of Burgundy replied by a letter in which, while disavowing the general principles that formed the major proposition of the argument of John Parvus, he maintained that the propositions condemned by the Bishop of Paris were not contained in the discourse.
In the United Kingdom, the current royal dukes are HRH the Prince of Wales, who is Duke of Cornwall and Duke of Rothesay; HRH the Duke of Edinburgh (Prince Philip), HRH the Duke of York (Prince Andrew), HRH the Duke of Gloucester (Prince Richard), and HRH the Duke of Kent (Prince Edward).
For example, when the current Duke of Gloucester and Duke of Kent are succeeded by their eldest sons, the Earl of Ulster and the Earl of St. Andrews, respectively, those peerages (or rather, the 1928 and 1934 creations of them) will cease to be associated with royalty.
The heir apparent to the Belgian throne is styled Duke of Brabant.