Hugh Mortimer and William la Zouche were brothers, and were only rather distantly related to the much more famous Mortimers of Wigmore, who became earls of March; this branch of the Mortimer family came
from Richard's Castle on the border of Shropshire and Herefordshire.
Hugh and William were born in the 1270s, and were the sons of Robert Mortimer and Joyce or Joice la Zouche. Hugh was named after their grandfather Hugh Mortimer, who died shortly before 28 November 1274 leaving his son Robert, aged '22 and more', as his heir to several manors in Herefordshire, Shropshire and Worcestershire.  Robert Mortimer was therefore born around the early 1250s, and died on 7 April 1287. Robert and Joyce's elder son and heir Hugh was allowed to take possession of his inheritance on 10 December 1295 as he was now 'of full age', meaning that he was born before 10 December 1274, probably not too long before, around the time that his paternal grandfather and namesake died. During his minority, Edward I had granted Hugh's wardship to William Beauchamp, earl of Warwick (d. 1298). 
Hugh Mortimer married a woman named Maud, who is known to have been a relative of Eleanor of Castile, queen of England, and of Eleanor's son Edward of Caernarfon, though the precise connection remains elusive. According to the Complete Peerage (vol. 9, pp. 264-5), Maud was a niece of William Marshal, and Edward of Caernarfon's extant correspondence of 1304/5 shows that he referred to her as nostre chere cosine Dame Maud de Mortimer du Chastel Richard, 'our dear cousin Lady Maud Mortimer of Richard's Castle'.
Hugh and Maud had two daughters, who were Hugh's heirs, and heirs to the Richard's Castle branch of the Mortimer family: Joan Mortimer, born in Caerphilly Castle on 24 November 1291, and Margaret Mortimer, born c. 14 September 1295. Hugh, born not too long before 10 December 1274, was a young father, barely seventeen when Joan was born. One of Joan's godfathers was Henry le Waleys, 'the Welshman'. Margaret's proof of age is missing so her place and exact date of birth are not known, but a reference on the Close Roll shows that the proof of age was held on or just before 18 September 1309. As well as being the heirs to their Mortimer father and grandfather, the Mortimer sisters were heirs to their father's uncle William Mortimer of Hamme, who died shortly before 2 November 1308.  They inherited lands in Herefordshire, Worcestershire, Shropshire, Wales, Northamptonshire, Essex, Hampshire and Devon.
Joan Mortimer married Thomas Bykenore sometime between 1 October 1304 and 27 June 1305, and Margaret Mortimer married Geoffrey Cornwall before 15 February 1308.  Geoffrey was a son of Sir Richard Cornwall (d. 1296/97), himself an illegitimate son of Richard, earl of Cornwall (1209-72), younger son of King John, brother of Henry III, and uncle of Edward I. That makes Geoffrey Edward II's second cousin, and his brother Edmund was knighted with Edward in 1306. Their sister Joan Cornwall married Sir John Howard of Norfolk and was an ancestor of the Howard dukes of Norfolk.
The sisters' father Hugh Mortimer of Richard's Castle died on 20 July 1304, probably not yet thirty years old, and peculiarly, his wife Maud was accused of poisoning both him and a man named Hugh de Kyngesmede or Kyngeshemede. She was pardoned at the request of Edward I's second wife Marguerite of France on 16 September 1305, and Marguerite's twenty-year-old stepson Edward of Caernarfon, Maud's kinsman, also took an interest in the case and sent numerous letters on the matter. One of Edward's letters reveals that he knew his mother Queen Eleanor had arranged Hugh and Maud Mortimer's marriage (nostre treschere dame e mere la fit marier).  Eleanor of Castile died on 28 November 1290, so Hugh and Maud's marriage must have been arranged before then, and as their first child was born in November 1291, the latest date their wedding can have taken place was February 1291. Maud Mortimer, cleared of the charges of murder, died sometime before 15 February 1308. 
The second Mortimer son, William, lived a much longer life than his older brother, and made two brilliant marriages. In 1298, he fought for Edward I at the battle of Falkirk as 'Sir William Mortimer of Richard's Castle' (Dns Willelmus de Mortuo Mari de Castro Ricardi), but by the autumn of 1304 had adopted his mother Joyce's name and began calling himself 'la Zouche'.  He often appears on record as 'William la Zousche de Mortuo Mari'. William's date of birth is not known, but his brother Hugh was almost certainly born in 1274, and as William was already a knight by the time of the battle of Falkirk in 1298, he must have been born before 1280. William acquired the Leicestershire manor of Ashby de la Zouch from his kinsman Alan la Zouche (d. 1314) on 20 October 1304, apparently an important factor in his decision to change his name. 
In contrast to his elder brother, a teenage husband and father, William la Zouche remained unmarried until 1316, when he wed Alice Toeni, dowager countess of Warwick and heir of the Toeni family. William must have been in his late thirties by then, perhaps even forty. Edward II granted the couple a licence to marry on 26 October 1316 in exchange for a payment of 500 marks.  Alice had been married twice before. She was the widow of Sir Thomas Leybourne (d. 1307), with whom she had a daughter Juliana, Lady Hastings and countess of Huntingdon (1303/4-1367), and of Guy Beauchamp, earl of Warwick (d. August 1315), with whom she had several children including Guy's heir Thomas, earl of Warwick (1314-69). Alice and Guy's son Thomas Beauchamp remained in her and William's custody until 20 July 1318, when Edward II gave Thomas's marriage rights to Roger Mortimer of Wigmore (later the first earl of March) and ordered Alice and William to "deliver to him the body of the said heir, in their keeping, to be married."  Thomas Beauchamp, who was only four years old then, later married Roger's daughter Katherine Mortimer.
Alice Toeni and William la Zouche had two children: Alan la Zouche, William's heir, and Joyce, named after his mother. Alan was probably born not long before 15 November 1317, as Edward III allowed 'Alan la Zouche, son and heir of William la Zouche Mortimer' to enter his late father's lands on 15 November 1338, having taken his homage. He was said to be nineteen years old in his father's inquisition post mortem, held in March to May 1337, which fits well with a date of birth in c. November 1317, about a year after his parents' wedding. He died on 12 November 1346 in his late twenties.  Joyce la Zouche married John, Lord Botetourt (b. c. 1316/18) and had children; her brother Alan married a woman named Eleanor, whose identity is unknown, and with her had a son and heir, Hugh la Zouche, born on 29 September 1338 in Powick ('Poywyk'), Worcestershire.  Alan la Zouche might have named his son in honour of his father's older brother Hugh Mortimer (d. 1304); alternatively, it is possible that Hugh la Zouche's godfather was his father's stepbrother Hugh, Lord Despenser (1308/9-1349). For the Zouche-Despenser connection, see below.
Alice Toeni Leybourne Beauchamp la Zouche
died before 8 January 1325, leaving her eldest son Thomas Beauchamp as her heir (her eldest child was Juliana Leybourne Hastings, heir to her father but not her mother).  Marrying the countess of Warwick had been quite a coup for William la Zouche given that he was a younger son and not an heir, and his second marriage was even better: Eleanor de Clare, Lady Despenser, born in October 1292 as the eldest niece of Edward II, lady of Glamorgan, and one of the richest women in the country. William abducted Eleanor from Hanley Castle in Worcestershire not long before 26 January 1329; see my post about it. By 1329, he must have been over fifty years old.
Around 1330, Eleanor bore William a son, William the younger, half-brother of Alan and Joyce la Zouche, and also half-brother of Eleanor's many Despenser children, the eldest of whom was born in 1308 or 1309. William la Zouche the younger is, considering that he was a great-grandson of King Edward I, remarkably obscure; at some point before February 1361, he became a monk at Glastonbury Abbey in Somerset, and was still alive on 6 December 1390. His cousin Edward III granted the abbot of Glastonbury ten marks a year during William's lifetime, and his Despenser kin gave him an allowance of a hundreds shillings a year.  Rather curiously, William la Zouche the younger was a first cousin of Joan Mortimer Bykenore, who was born in 1291 and was about four decades older than he.
William la Zouche the father died on 28 February 1337, and Eleanor buried him in Tewkesbury Abbey in Gloucestershire, where her first husband Hugh Despenser the Younger and many of her Clare relatives and ancestors were also buried. She only outlived him by four months and died at the age of forty-four on 30 June 1337, and was also buried in Tewkesbury Abbey. William had made her an executor of his will, and as Eleanor buried him in her family's mausoleum, it would seem that they had made a success of their marriage, whether Eleanor had consented to it in January 1329 or not. William la Zouche's marriages to two women of much higher rank and much greater wealth than he would seem to imply that he was an attractive, appealing man.
1) CIPM 1272-91, no. 132.
2) CIPM 1272-91, nos. 640, 785; CCR 1288-96, pp. 72, 467.
3) CIPM 1300-07, no. 221; CIPM 1307-17, nos. 57, 66, 133; CCR 1307-13, pp. 97-8, 177-78.
4) CIPM 1300-07, no. 221; CIPM 1307-17, no. 57; CPR 1301-7, pp. 261, 265, 311, 321.
5) CPR 1301-7, pp. 378, 402, 486; Hilda Johnstone, Letters of Edward, Prince of Wales 1304-1305, pp. 34, 50-51, 58,, 75-6 etc.
6) CIPM 1307-17, no. 57; CFR 1307-19, p. 14.
7) Complete Peerage, vol. 12B, p. 957.
8) Feet of Fines for Leicestershire, CP 25/1/285/25, no. 298; CFR 1307-19, p. 191; CCR 1313-18, pp. 59-61.
9) CFR 1307-19, p. 308.
10) CFR 1307-19, p. 369.
11) CCR 1337-9, p. 559; CIPM 1336-46, nos. 112, 662.
12) CIPM 1352-60, nos. 592, 644.
13) CFR 1319-27, pp. 324-5; CIPM 1317-27, no. 611.
14) CPR 1358-61, p. 538; CFR 1377-83, p. 46; CFR 1383-91, p. 346.