Henry of Grosmont, 1st Duke of Lancaster in the context of "House Lancaster"

The House of Lancaster was a cadet branch of the royal House of Plantagenet. The first house was created when King Henry III of England created the Earldom of Lancaster—from which the house was named—for his second son Edmund Crouchback in 1267. Edmund had already been created Earl of Leicester in 1265 and was granted the lands and privileges of Simon de Montfort, 6th Earl of Leicester, after de Montfort's death and attainder at the end of the Second Barons' War. When Edmund's son Thomas, 2nd Earl of Lancaster, inherited his father-in-law's estates and title of Earl of Lincoln he became at a stroke the most powerful nobleman in England, with lands throughout the kingdom and the ability to raise vast private armies to wield power at national and local levels. This brought him—and Henry, his younger brother—into conflict with their cousin King Edward II, leading to Thomas's execution. Henry inherited Thomas's titles and he and his son, who was also called Henry, gave loyal service to Edward's son King Edward III.

The second house of Lancaster was descended from John of Gaunt, a Plantagenet prince, who married the heiress of the first house, Blanche of Lancaster. Edward III married all his sons to wealthy English heiresses rather than following his predecessors' practice of finding continental political marriages for royal princes. Henry of Grosmont, 1st Duke of Lancaster, had no male heir so Edward married his son John to Henry's heiress daughter and John's third cousin Blanche of Lancaster. This gave John the vast wealth of the House of Lancaster. Their son Henry usurped the throne in 1399, creating one of the factions in the Wars of the Roses. There was an intermittent dynastic struggle between the descendants of Edward III. In these wars, the term "Lancastrian" became a reference to members of the family and their supporters. The family provided England with three kings: Henry IV (r. 1399–1413), Henry V (r. 1413–1422), and Henry VI (r. 1422–1461 and 1470–1471).

The Most Noble Order of the Garter is an order of chivalry founded by King Edward III of England in 1348. The most senior order of knighthood in the British honours system, it is outranked in precedence only by the decorations of the Victoria Cross and the George Cross. The Order of the Garter is dedicated to the image and arms of Saint George, England's patron saint.

Appointments are at the Sovereign's sole discretion, typically made in recognition of national contribution, service to the Crown, or for distinguished personal service to the Monarch. Membership of the order is limited to the sovereign, the Prince of Wales, and no more than 24 living members, or Companions. The order also includes Supernumerary Knights and Ladies (e.g., members of the British royal family and foreign monarchs).

Blanche of Lancaster (25 March 1342 – 12 September 1368) was a member of the English-French royal House of Lancaster and the daughter of the kingdom's wealthiest and most powerful peer, Henry of Grosmont, 1st Duke of Lancaster. She was the first wife of John of Gaunt, the mother of King Henry IV, and the grandmother of King Henry V of England.