John of Gaunt, Earl of Richmond, 4th son of King Edward III, was b. 1340, styled of Gaunt from the place of his birth, who had been created Earl of Richmond in 1342, was advanced to the Dukedom of Lancaster by his father, Edward III, in the 36th year of his reign. After the decease of his 1st wife, Blanch, the great heiress of the Duke of Lancaster, he m. Constance, elder dau. and co-heiress of Peter, King of Castile, and in her right assumed the title of King of Castile and Leon, in which regal dignity, as well as in those of Duke of Lancaster, Earl of Richmond, Derby, Lincoln, and Leicester, he had summons to parliament; he was likewise Duke of Aquitaine and a knight of the Garter. On the decease of Edward III, this prince was joined in the administration of affairs during the minority of his nephew, Richard II. He subsequently attempted the conquest of Spain at the head of a fine army, and landing at the Groyne, advanced to Compostella, where he was met by John, King of Portugal, between whom and his eldest dau., the Lady Philippa, a marriage was concluded. Thence he marched into Castile and there ratified a treaty of peace, by which he abandoned his claim to the throne of Castile and Leon in consideration of a large sum of money and the marriage of Henry, Prince of Asturias, with his only dau. by his 2nd wife, the Lady Katherine Plantagenet. In the latter part of his life he dwelt in retirement, having incurred the displeasure of King Richard by a motion which he had made in parliament that his son, Henry of Bolingbroke, should be declared heir to the crown. He d. at Ely House, Holborn, in 1399.
John of Gaunt m. 1st, in 1359, Lady Blanche Plantagenet, the eventual heiress of the Duke of Lancaster, and had by her, Henry, Philippa, and Elizabeth. He m. 2ndly, Constance, elder dau. and co-heir of Peter, King of Castile, and by her had an only dau., Katherine. The duke m. 3rdly, in 1396, Catherine, dau. of Sir Payn Roet, Guyenne King of Arms, and widow of Sir Otho de Swynford, Knt., by whom, before marriage, he had issue, John, Henry, Thomas, and Joan. These [last] children were legitimated by act of parliament for all purposes, save succession to the throne, in the 20th Richard II and derived their surname from the castle of Beaufort, the place of their birth. John of Gaunt, was s. by his eldest son, Henry Plantagenet, b. 1366, surnamed of Bolingbroke, Earl of Hereford, who, upon the deposition of Richard II, was called to the throne as King Henry IV, when his great inheritance, with the Dukedom of Lancaster, and the Earldoms of Hereford, Derby, Lincoln, and Leicester, merged in the crown. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages, Burke's Peerage, Ltd., London, 1883, p. 432, Plantagenet, Earls of Chester, &c.]
----------
John OF GAUNT, DUKE OF LANCASTER, also called (1342-62) EARL OF RICHMOND, or (from 1390) DUC (duke) D'AQUITAINE (b. March 1340, Ghent--d. Feb. 3, 1399, London), English prince, fourth but third surviving son of the English king Edward III and Philippa of Hainaut; he exercised a moderating influence in the political and constitutional struggles of the reign of his nephew Richard II. He was the immediate ancestor of the three 15th-century Lancastrian monarchs, Henry IV, V, and VI. The term Gaunt, a corruption of the name of his birthplace, Ghent, was never employed after he was three years old; it became the popularly accepted form of his name through its use in Shakespeare's play Richard II.
Through his first wife, Blanche (d. 1369), John, in 1362, acquired the duchy of Lancaster and the vast Lancastrian estates in England and Wales. From 1367 to 1374 he served as a commander in the Hundred Years' War (1337-1453) against France. On his return he obtained the chief influence with his father, but he had serious opponents among a group of powerful prelates who aspired to hold state offices. He countered their hostility by forming a curious alliance with the religious reformer John Wycliffe. Despite John's extreme unpopularity, he maintained his position after the accession of his ten-year-old nephew, Richard II, in 1377, and from 1381 to 1386 he mediated between the King's party and the opposition group led by John's younger brother, Thomas of Woodstock, earl of Gloucester.
In 1386 John departed for Spain to pursue his claim to the kingship of Castile and Leon based upon his marriage to Constance of Castile in 1371. The expedition was a military failure. John renounced his claim in 1388, but he married his daughter, Catherine, to the young nobleman who eventually became King Henry III of Castile and Leon.
Meanwhile, in England, war had nearly broken out between the followers of King Richard II and the followers of Gloucester. John returned in 1389 and resumed his role as peacemaker.
His wife Constance died in 1394, and two years later he married his mistress, Catherine Swynford. In 1397 he obtained legitimization of the four children born to her before their marriage. This family, the Beauforts, played an important part in 15th-century politics. When John died in 1399, Richard II confiscated the Lancastrian estates, thereby preventing them from passing to John's son, Henry Bolingbroke. Henry then deposed Richard and in September 1399 ascended the throne as King Henry IV. [Encyclopædia Britannica CD '97]