the Battle of Nájera. Edward and Peter fell out when Peter was unable to reimburse Edward's military expenses, leaving him bankrupt. The Plantagenets continued to interfere, and John of Gaunt, 1st Duke of Lancaster, the Black Prince's brother, married Peter's daughter Constance, claiming the Crown of Castile in her name. He invaded with an army of 5,000 men; however, fighting was inconclusive, before Gaunt agreed to a treaty with King Juan of Castile. Terms of the treaty included the marriage of John of Gaunt's daughter Katherine to Juan's son, Enrique. Charles V of France maintained the terms of the treaty of Brétigny but encouraged others in Aquitaine to challenge the authority of the Plantagenets in Aquitaine. The prince, who had suffered a debilitating illness for nearly a decade which often restricted his movement to being carried in a litter, returned to England, where he soon died. John of Gaunt assumed leadership in France with limited success, and peace negotiations over several years were inconclusive. Descendants of Edward III The marriage of Edward III and Philippa of Hainault produced thirteen children and thirty-two grandchildren: Edward (1330–1376)married his cousin Joan of Kent, a granddaughter of Edward I, with whom he had two sons: Edward (1365–1371/2) Richard (1367–1400) Isabella (1332–1382)married Enguerrand VII, Lord of Coucy, and had two daughters: Marie Philippa Joan (1335–1348) William (1334/6–1337) Lionel (1338–1368)had one daughter with Elizabeth de Burgh: Philippa (1355–1378/81)through Philippa, the House of York, by cognatic kinship, asserted that its claim to the throne was superior to the House of Lancaster's. Philippa's granddaughter and heir, Anne Mortimer, married Richard of Conisburgh, 3rd Earl of Cambridge, the Duke of York's heir. The earls of Northumberland and Clifford, significant supporters of the Lancasters during the Wars of the Roses, were descendants of Philippa through her other daughter, Elizabeth Mortimer. John of Gaunt (1340–1399)married Blanche of Lancaster, the heiress to the duchy of Lancaster and a direct descendant of Henry III, and had seven children with her: Philippa (1360–1415)married John I of Portugal. John (c. 1362/1364)died as an infant. Elizabeth (1364–1426)married John Hastings, 3rd Earl of Pembroke; John Holland, 1st Duke of Exeter; and John Cornwall, 1st Baron Fanhope; respectively. Edward of Lancaster (1365–1365) John of Lancaster (1366)died as an infant. Henry (1367–1413) Isabella of Lancaster (b. 1368)died as a child. After Blanche's death in 1369, John married Constance of Castile, trying unsuccessfully to obtain the throne of Castile. The