On 15 August 1316, Isabella of France gave birth to her and Edward's second son John of Eltham, later earl of Cornwall. I suspect that John was named in honour of the new pope, John XXII, who was elected by the cardinals at Avignon on 5 August. News of his election reached England about the time of little John's birth; Edward II gave a pound to Lawrence de Hibernia, the messenger who brought him the news in Yorkshire, on 17 August 1316, and Queen Isabella 250 miles further south in Kent had presumably heard the news a few days earlier.
On 16 August 1284, Isabella's parents the future Philip IV of France and Joan, queen of Navarre, and countess of Champagne and Brie, got married. Philip was fifteen or sixteen, Joan eleven or twelve. Their eldest child, or at least their eldest son, was born on 4 October 1289: Louis X of France.
On 19 August 1284, Edward II's elder brother Alfonso of Bayonne died suddenly at the age of ten (he was born in Bayonne in November 1273 and named after his uncle and godfather Alfonso X of Castile). This made the four-month-old Edward of Caernarfon heir to the throne. Alfonso himself had become heir to the throne at the age of eleven months in October 1273 on the death of their six-year-old brother Henry, the second son of Edward I and Eleanor of Castile. Alfonso's death seems to have come as a great shock to his parents, as Edward I was arranging a marriage for him with a daughter of the count of Holland. Eleanor of Castile was buried with his heart after her death in November 1290.
Also on 19 August, in 1315, Edward's twenty-five-year-old brother-in-law Louis X of France married his second queen Clemence of Hungary, five days after the death (or the murder?) of his adulterous first wife Marguerite of Burgundy at Château Gaillard. Clemence was crowned queen of France at Rheims on 24 August. One of Edward II's scribes made an embarrassing mistake a few months later, and addressed her in a letter as 'Queen Elizabeth'. Oooops. Louis died suddenly on 5 June 1316, and on 15 November Clemence gave birth to his posthumous son King John I, who sadly lived for only five days.
On 24 August 1325, Edward wrote to his last remaining brother-in-law Charles IV telling him that he was ill and thus would not be able to travel to France to pay homage to Charles for his French possessions of Gascony and Ponthieu, as he was meant to do on 29 August. This is unlikely to have been a genuine illness, but rather a diplomatic one as Edward stalled for time. After weeks of prevaricating, on 12 September he sent his son to France in his place, which would with hindsight have been the worst thing he could have done. At the time, however, he really had little other option.
On 27 August 1320, Edward wrote to the king of Cyprus and titular king of Jerusalem, Henri de Lusignan, asking him to protect three Dominican friars going to preach to the Saracens. Henri was Edward's third cousin twice removed via common descent from Eleanor of Aquitaine, Henri being descended from Eleanor's eldest child Marie of France; he was also the great-great-grandson of the famous Balian Ibelin.
On 28 August 1311, Edward II paid £113 "for the expenses and preparations made for the burial of the body of the Lady Eleanor, the king's sister" at Beaulieu Abbey in Hampshire. Eleanor was his half-sister and only five years old (born 4 May 1306) at her death, the youngest child of Edward I and Marguerite of France. Edward I was almost sixty-seven at the time of Eleanor's birth, and she was at least forty-five or so years younger than his eldest child. Edward I's eldest great-grandchild, Hugh, Lord Despenser (child of Eleanor de Clare and Hugh Despenser the Younger) was born in 1308 or 1309: only two or three years' age difference between a child and a great-grandchild.
29 August, the feast of the Beheading of St John the Baptist, in 1321 was the deadline for the two Hugh Despensers to leave England into perpetual exile, at the demand of their baronial enemies whom Edward II took to calling the Contrariants. Hugh the Younger appears to have left a few days after the deadline, apparently accompanied by the king, and became a pirate in the English Channel.