And now some new information. I've recently learned that, on 31 July 1291 when he was seven, Edward of Caernarfon was betrothed to Blanche of France. Blanche was the daughter of the late King Philip III by his second wife Marie of Brabant, and thus the half-sister of Philip IV, full sister of Marguerite (second wife of Edward I and stepmother of Edward II) and aunt of Edward II's Queen Isabella.
Blanche's date of birth is unknown, but she was several years older than little Edward. Her parents married on 21 August 1274, and her brother Louis, Count of Évreux, was born on 3 May 1276. Louis was on very close terms with Edward II, and it was to him that Edward sent his famous 1305 letter about trotting palfreys and wild Welshmen. Louis travelled to England in 1312 to mediate between Edward and the barons after Gaveston's murder, and was one of Edward III's godfathers.
Blanche and her sister Marguerite, Queen of England, were born sometime between 1278 and 1282. It's unclear which sister was the elder. Thomas Costain in his The Three Edwards relates a story that Edward I wished to marry Blanche, who was far more beautiful than her sister, even showing a willingness to give up Gascony (also known as Aquitaine) in exchange, but was tricked into marrying Marguerite instead. This story, repeated on Marguerite's Wikipedia page, seems incredibly unlikely, especially given that Blanche had been betrothed to Edward I's son, and besides, the notion that Edward I would have given up Gascony to marry Blanche is laughable.
In May 1294, Blanche's half-brother Philip IV confiscated Gascony, and her betrothal to Edward was broken off. Edward was ten when his second betrothal fell through, Blanche somewhere between twelve and sixteen. She was offered instead to John of Hainault, Count of Ostrevant (killed at the battle of Courtrai in 1302), who was the elder brother of Count William of Hainault, father of Edward III's wife Queen Philippa. This alliance also faltered, and she finally married, in Paris on 29 May 1300, Rudolf III, Duke of Austria, later King of Bohemia and titular King of Poland. Her sister Marguerite, now Queen of England, gave birth to her first child Thomas of Brotherton three days after Blanche's wedding.
Queen/Duchess Blanche died on 19 March 1306, and was buried in the Minoritenkirche in Vienna. She had given birth to a daughter, who died in infancy. Duke Rudolf married secondly Ryksa Elźbieta of Poland, but died childless on 4 July 1307 (three days before Edward I).http://edwardthesecond.com/familyofedwardii/betrothals2.html
His title Rudolph III is of Austria and Rudolph I of Bohemia