Hugh Despenser the Elder, created earl of Winchester by Edward II in 1322, was probably the only man of rank who remained completely loyal to Edward from the beginning to the end of his reign. He was destined to end his long life executed by Roger Mortimer and Isabella of France at Bristol on 27 October 1326, his head taken afterwards on a spear to adorn the walls of Winchester Castle and his body fed to dogs. Hugh was sixty-five at the time of this grotesque fate, born on 1 March 1261.  His father Sir Hugh Despenser, justiciar of England and a staunch supporter of Simon de Montfort, was killed at the battle of Evesham in August 1265 fighting against the future Edward I, but luckily for the four-year-old boy's future, his maternal grandfather Sir Philip Basset, who lived until 1271, was a royalist baron and a personal friend of Henry III's brother Richard of Cornwall. Hugh's widowed mother Aline, Philip Basset's only child and heir, married secondly Roger Bigod (born c. 1245), earl of Norfolk, and died in early April 1281. (It's interesting to note that even during her second marriage, Aline continued to use the name 'Despenser', even though her second husband was of a higher rank than her first; anyone who thinks the Despensers were nobodies, please take note.) The Bigod earls' biographer Marc Morris relates an interesting story whereby Roger Bigod attempted to wrest control of his late wife's inheritance out of his stepson's hands by pretending that Aline had borne him a child, who had taken a breath before dying. A living child meant, by the contemporary custom known as the 'courtesy of England', that Earl Roger would have gained a life interest in his wife's entire estate. Hugh Despenser vigorously contested the claim, and Roger was forced to drop it.  (He died childless in 1306, having married secondly the count of Holland and Hainault's daughter Alicia; his patrimony passed eventually to Edward II's half-brother Thomas of Brotherton.)
Hugh was twenty when his mother Countess Aline died, and on 28 May 1281, a few weeks after her death, Edward I granted his marriage to William Beauchamp, earl of Warwick. On 2 April 1282, shortly after he came of age (i.e. twenty-one), Hugh bought his marriage from Warwick for 1600 marks.  Though no-one could have known it then, his future wife was Warwick's daughter Isabel, who exactly two months before this purchase had given birth to her eldest child, Maud Chaworth, by her husband Patrick. Patrick died in July 1283 leaving Maud, his only child, as his heir, and by 2 March 1297 she had married Edward I's nephew Henry of Lancaster (younger brother of Thomas).  At an uncertain date, probably in 1286, Hugh Despenser and Isabel Beauchamp married without a royal licence, for which they were fined 2000 marks by the king (Edward acquitted them of the payment in November 1287, but by then they had already paid almost £1000 of it). 
I've seen Hugh Despenser the Elder called a nobody, a mere humble knight of no great background; one book even states, incredibly, that Hugh and his son were "not members of a baronial family," a jaw-dropping statement. Hugh the Elder was stepson of the earl of Norfolk and son-in-law of the earl of Warwick. Given that his father had died in rebellion against the Crown, he'd done remarkably well for himself, and, his marriage without royal licence notwithstanding, was high in Edward I's favour. He and Isabel Beauchamp had six children: Hugh, Philip, Aline, Isabel, Margaret and Elizabeth, who were via their elder half-sister Maud Chaworth brothers- and sisters-in-law of Edward I's nephew Henry of Lancaster, whose own half-sister Jeanne was queen of Navarre in her own right and queen of France by marriage. In 1306, Edward I demonstrated his appreciation of Hugh Despenser the Elder's loyalty and abilities by arranging the marriage of Hugh's heir Hugh the Younger to his eldest granddaughter Eleanor de Clare - further evidence, if it were needed, that the claim that the Despensers were not a baronial family is utter nonsense. Their wedding took place in the king's presence at Westminster on 26 May 1306, the day after Eleanor's first cousin Jeanne de Bar married the earl of Surrey and four days after Hugh, Surrey and many others were knighted with Edward of Caernarfon.
Eleanor was thirteen and a half at the time of her marriage (born in October or November 1292), Hugh probably between sixteen and nineteen (his date of birth is unknown, somewhere between 1287 and 1290). Somewhat confusingly, an entry on the Patent Roll of 14 June 1306 talks of a "[g]rant to Hugh le Despenser, son of Hugh le Despenser, between whom and Eleanor daughter of Gilbert, sometime earl of Gloucester and Hertford, the king's niece [actually granddaughter], a marriage is contracted, with the king's and the said Hugh's assent...".  From other evidence, however - gifts from Edward I to Eleanor and his hiring of minstrels to play at the wedding, and the chronicle of Pierre Langtoft - it is apparent that the couple had already married some weeks before.
Isabel Beauchamp died on or shortly before 30 May 1306, on which date the escheator was ordered to take into the king's hands "the lands which Isabel late the wife of Hugh le Despenser, deceased, held with Hugh in chief in frank marriage of the gift of William de Bello Campo [Beauchamp], earl of Warwick, deceased."  That week in late May 1306 must have been a strange one for Hugh the Younger: he was made a knight and got married, but lost his mother. As with almost all women of the era, Isabel is a shadowy figure about whom little is known. Something of her personality emerges in a petition presented at the beginning of Edward III's reign, when William de Odyham complained that the younger Hugh had removed him from his job as parker of Odiham Castle in Hampshire because Odyham had once "levied hue and cry upon Isabel the said Hugh's mother, who was taking five bucks in the park without warrant." 
Hugh Despenser the Elder never remarried and remained a widower for a little over twenty years. Hugh the Younger and Eleanor de Clare were married for almost exactly the same period, and had at least ten children together. One of the two Hughs was most probably the father of Nicholas de Litlyngton, abbot of Westminster from 1362 to 1386 (see Susan Higginbotham's post). Hugh the Elder seems not to have been on good terms during Edward II's reign with his brother-in-law Guy Beauchamp, earl of Warwick, the man who in 1312 abducted Piers Gaveston, of whom Hugh was a staunch supporter.
1) Calendar of Inquisitions Post Mortem, vol. 2, nos. 101, 389; Calendar of Fine Rolls 1272-1307, pp. 149, 152.
2) Marc Morris, The Bigod Earls of Norfolk in the Thirteenth Century (2005), p. 125.
3) Calendar of Patent Rolls 1272-1281, p. 439; Calendar of Close Rolls 1279-1288, p. 184.
4) Cal Pat Rolls 1292-1301, p. 239.
5) Cal Close Rolls 1279-1288, p. 462; Martyn Lawrence, 'Rise of a Royal Favourite: the Early Career of Hugh Despenser the Elder', in Gwilym Dodd and Anthony Musson, eds., The Reign of Edward II: New Perspectives (2006), p. 208.
6) Cal Pat Rolls 1301-1307, p. 443.
7) Cal Fine Rolls 1272-1307, p. 538.
8) Calendar of Inquisitions Miscellaneous (Chancery) 1308-1348, no. 988; The National Archives SC 8/160/7986