Here's a post about Edward II's cousin John of Lancaster. Although he was a grandson of Henry III, king of England, a great-grandson of Louis VIII, king of France, the younger half-brother of Juana I, queen regnant of Navarre and queen consort of France, and the uncle of Edward II's queen Isabella and her brothers Louis X, Philip V and Charles IV of France, John is rather obscure.
John was the third and youngest son of Edmund of Lancaster (1245-96), who was the younger son of Henry III and the only brother of Edward I, and his second wife Blanche of Artois (c. 1245/48-1302), dowager queen of Navarre. Edmund and Blanche's eldest son and heir Thomas might have been born on 29 December 1277 or shortly afterwards, and their second son Henry, his brother Thomas's heir in 1322 and ancestor of all the later Lancasters, in c. 1280. John of Lancaster was born sometime before May 1286, when his paternal grandmother Eleanor of Provence, Henry III's widow and the dowager queen of England, bequeathed her claim to the county of Provence to her three Lancaster grandsons. [Calendar of Patent Rolls 1281-92, p. 243]
Edmund of Lancaster, earl of Lancaster and Leicester, arranged the marriage of his second son Henry to Maud Chaworth, older half-sister of Hugh Despenser the Younger and sole heir of her late father, the Marcher lord Patrick Chaworth, in December 1291. [CPR 1281-92, p. 464] In the usual oh so terribly romantic fashion of medieval arranged marriages, John of Lancaster was named as Maud's substitute future husband in case his brother Henry died. (John was the third son, not the second, as stated.)
Edmund died on 5 June 1296. The bulk of his vast estate went to his eldest son Thomas, though in August 1292 Edmund had arranged for his four castles in Wales plus the Gloucestershire manors of Rodley and Minsterworth to pass to his second son Henry. Thomas was named as heir to these estates if Henry died without children, with John as next heir. [Calendar of Charter Rolls 1257-1300, p. 423; The National Archives DL 10/191]
To my knowledge, John of Lancaster held no lands in England or Wales, though somehow, and I'm not sure how, he acquired the French lordship of Beaufort, now called Montmorency-Beaufort. It's in the region of Champagne, between Troyes and Nancy, and is 115 miles east of Paris. John's mother Blanche of Artois's first husband Enrique I (d. 1274) was count of Champagne as well as king of Navarre, and the county passed to John's half-sister Queen Juana (b. 1273), countess of Champagne in her own right, a fact which presumably had something to do with John's acquisition of a lordship there. John also appears to have held the lordships of Soulaines, 'Bargencourt' (which probably means Boulancourt) and Nogent l'Artaud, or to be precise, in 1329 his brother and heir Henry wrote to King Philip VI of France about goods which he owned in those places. [Documents Parisiens du Règne de Philippe VI de Valois (1328- 1350): Extraits des Registres de la Chancellerie de France, ed. Jules Viard, vol. 1, pp. 84-5]Considering that when they were growing up, the three Lancaster brothers were nephews of the king of England and brothers-in-law of the king of France, Philip IV (who married their half-sister Juana of Navarre and Champagne in 1284), and thus could hardly have been better connected, their childhoods are almost completely obscure. The household account, in England, of Jan of Brabant survives for a few months in 1292/93; he was the son and heir of Jan I, duke of Brabant, and married the Lancaster brothers' cousin Margaret, one of Edward I's daughters, in 1290. Thomas and Henry of Lancaster appear several times in the account; John of Lancaster does not. ['Account of the Expenses of John of Brabant and Henry and Thomas of Lancaster, 1292-3', Camden Miscellany, 1853, ed. Joseph Burtt] During the same time period, Thomas and Henry are also mentioned several times, as 'Thomas and Henry the sons of Lord Edmund', in the extant account of their cousin Edward of Caernarfon, but John is not.
It strikes me as highly likely that John of Lancaster spent most of his life in his mother Blanche of Artois's native France, and as he held lands there, he might well have been born in France (his brothers Thomas and Henry, who inherited lands in England, must, by English inheritance law of the time, have been born in England itself or in another of the territories ruled by the king of England).
Unlike his two older brothers, John married a French noblewoman. She was Alix de Joinville, youngest child of the chronicler and historian Jean de Joinville, lord of Joinville, and his second wife Alix, daughter of the lord of Reynel. Jean de Joinville lived a remarkably long life. He was born around 1224 or 1225 - he was excused from fighting in the battle of Taillebourg in 1242 as he hadn't been knighted yet - and did not die until December 1317. I have no idea when Alix de Joinville was born, but she likely wasn't too much older than John of Lancaster, and was probably born when her father was in his fifties. Her parents married in 1262, and her own first marriage to Jean, lord of Arcis-sur-Aube - which is just twenty miles from John of Lancaster's lordship of Beaufort - was arranged in 1300. Jean d'Arcis-sur-Aube died childless in 1307, the same year that John of Lancaster's cousin Edward II succeeded John's uncle Edward I as king of England. Alix de Joinville herself died in or after 1336, and her brother Anseau in 1342 or 1343. [Information from the Medieval Lands project on the Foundation for Medieval Genealogy site]
John of Lancaster's half-sister Juana I, queen regnant of Navarre, queen consort of France and countess of Champagne, obviously knew Alix's father Jean de Joinville: she commissioned him to write a history of Louis IX of France (r. 1226-70), who was her husband Philip IV's grandfather and was also the great-uncle of herself and her three Lancaster half-brothers (their mother Blanche of Artois was the daughter of Louis IX's brother Robert, count of Artois). It's possible therefore that John knew the Joinville family via Queen Juana, though Juana can't have arranged his marriage to Alix as she died in 1305, two years before Alix's first husband Jean d'Arcis-sur-Aube.
John and Alix de Joinville were married by July 1312 when a grant made to the abbey of Chapelle-aux-Planches by Jehans de Lancastre, sires de Biaufort [lord of Beaufort], et Aalis de Joinville is recorded. Alix is called John's 'loyal consort and wife' (sa loiaulx compaigne et espouse). To put the date into context, that's the month after Piers Gaveston, beloved of John's cousin Edward II, was killed in Warwickshire, and four months before John's niece Isabella, queen of England, Juana's daughter, gave birth to the future Edward III.
A slightly later grant by John, calling himself Jehan de Lancastre and his wife Aalis de Joinville, is also extant. It's interesting to see that he called Alix by her maiden name, not 'de Lancastre' or 'd'Arcis-sur-Aube' for her first husband. [Mémoires de la Société d’Agriculture, Commerce, Sciences & Arts du Département de la Marne, 1883-84, pp. 151-2] On another occasion, in October 1312, he referred to himself as Jehans de Lancastre and to Alix as 'our beloved and loyal consort Aelips de Joinville'. Alix put her own seal to the document as well, calling herself Aleyps de Joinville and John 'my dearest and loyal lord and companion, Jehans de Lancastre'. [Collection des Principaux Cartulaires du Diocèse de Troyes, vol. 4, pp. 78-80]
John of Lancaster died childless sometime before 13 June 1317, a few months before his father-in-law Jean de Joinville finally passed away in his nineties, in the reign of his nephew Philip V of France, Queen Juana's second son. On that date, his cousin Edward II wrote to Philip V, asking him to postpone the required homage of John's brother and heir Henry until after the next feast of the Purification, i.e. 2 February 1318. Edward's letter indicates that John had owned lands in Chaumpayn & Brye, Champagne and Brie (yummy!). Henry of Lancaster left England for France sometime after 1 June 1318, and on 28 September that year, Edward II stated that he 'is staying in France to obtain the inheritance in that land which by the death of John de Lancastre, his brother, descended to him.' [Foedera 1307-27, p. 334; CPR 1317-21, pp. 145-46, 153, 217] Just as I'm not sure how John obtained his French lands in the first place, I'm also not sure why Henry, and not the eldest Lancaster brother Thomas, earl of Lancaster and Leicester, was John's heir to them. John was in his early or mid-thirties when he died, and his older brothers outlived him; Thomas was executed by Edward II in 1322, and Henry, who was Thomas's heir as well as John's, died in his mid-sixties in 1345.
The lordship of Beaufort thus passed in 1317 to Henry of Lancaster, later earl of Lancaster and Leicester; then on Henry's death in 1345 to his son Henry of Grosmont, first duke of Lancaster; then on Duke Henry's death in 1361 to his daughter Blanche, who married John of Gaunt. In the 1370s, Gaunt had four children with Katherine Swynford who were given the last name Beaufort.