Before 04 Oct 1379 [his father] John I King Castile (age 21) and [his mother] Eleanor Barcelona Queen Consort Castile (age 21) were married. She by marriage Queen Consort Castile. She the daughter of [his grandfather] Peter IV King Aragon (age 60) and [his grandmother] Eleanor Barcelona Queen Consort Aragon. He the son of [his grandfather] Henry "Fratricide" II King Castile and [his grandmother] Juana Manuel Queen of Castile (age 40). They were third cousin once removed. He a great x 5 grandson of King Henry "Curtmantle" II of England.

On 04 Oct 1379 Henry III King Castile was born to John I King Castile (age 21) and Eleanor Barcelona Queen Consort Castile (age 21) at Burgos [Map].

On 13 Sep 1382 [his mother] Eleanor Barcelona Queen Consort Castile (age 24) died.

Before 17 Sep 1388 Henry III King Castile (age 8) and Catherine of Lancaster Queen Consort Castile (age 15) were married at Palencia Cathedral [Map]. She by marriage Queen Consort Castile. She the daughter of John of Gaunt 1st Duke Lancaster (age 48) and Constance of Castile Duchess of Lancaster (age 34). He the son of John I King Castile (age 30) and Eleanor Barcelona Queen Consort Castile. They were half second cousins. She a granddaughter of King Edward III of England.

Chronicle of Adam of Usk. 17 Sep 1388. The [his father-in-law] duke of Lancaster (age 48) also, claiming the kingdom of Spain in right of his [his mother-in-law] wife (age 34), sailed to that country two years after, with another crusade; and there he lost by the same sickness many of the nobles of the realm of England, and, I may say, the flower of its youthful chivalry. Yet he made peace with the king of Spain, receiving a duchy for the term of his life, and a large sum of gold for his outlay, and giving his [his wife] daughter (age 15) in marriage to the king’s eldest son (age 8); and so he returned to England¹.

Note 1. There is no mention of the duchy in the other chronicles. By the terms of the treaty, Catherine of Lancaster married Henry, prince of the Asturias, in 1393. The duke received the sum of 200,000 crowns and a pension for the lives of himself and his duchess.

On 09 Oct 1390 [his father] John I King Castile (age 32) died. His son Henry III King Castile (age 11) succeeded III King Castile.

In 1391 Robert Ferrers (age 18) and [his illegitimate sister-in-law] Joan Beaufort Countess of Westmoreland (age 12) were married at Beaufort en Vallée [Map]. She the illegitmate daughter of [his father-in-law] John of Gaunt 1st Duke Lancaster (age 50) and Katherine Roet Duchess Lancaster (age 40). She a granddaughter of King Edward III of England.

Before 29 Nov 1396 Ralph Neville 1st Earl of Westmoreland (age 32) and [his illegitimate sister-in-law] Joan Beaufort Countess of Westmoreland (age 17) were married. She by marriage Baroness Neville Raby. She the illegitmate daughter of [his father-in-law] John of Gaunt 1st Duke Lancaster (age 56) and Katherine Roet Duchess Lancaster (age 46). He a great x 5 grandson of King Henry "Curtmantle" II of England. She a granddaughter of King Edward III of England.

On 27 Nov 1397 [his illegitimate brother-in-law] John Beaufort 1st Marquess Somerset and Dorset (age 24) and Margaret Holland Duchess Clarence (age 12) were married. She by marriage Countess Somerset. She the daughter of Thomas Holland 2nd Earl Kent and Alice Fitzalan Countess Kent (age 47). He the illegitmate son of [his father-in-law] John of Gaunt 1st Duke Lancaster (age 57) and Katherine Roet Duchess Lancaster (age 47). They were half third cousins. He a grandson of King Edward III of England. She a great x 2 granddaughter of King Edward I of England.

On 10 Nov 1399 King Henry V of England (age 13) was created 1st Duke Lancaster by [his brother-in-law] King Henry IV of England (age 32).

In 1400 John Cornwall 1st Baron Fanhope 1st Baron Milbroke (age 36) and [his sister-in-law] Elizabeth Lancaster Duchess Exeter (age 36) were married. She the daughter of [his father-in-law] John of Gaunt 1st Duke Lancaster and Blanche Duchess of Lancaster. He a great x 3 grandson of King John of England. She a granddaughter of King Edward III of England.

On 14 Sep 1401 [his daughter] Maria Trastámara Queen Consort Aragon was born to Henry III King Castile (age 21) and [his wife] Catherine of Lancaster Queen Consort Castile (age 28). She a great granddaughter of King Edward III of England. Coefficient of inbreeding 2.15%.

In 1403 [his daughter] Catherine Trastámara was born to Henry III King Castile (age 23) and [his wife] Catherine of Lancaster Queen Consort Castile (age 29). She a great granddaughter of King Edward III of England. Coefficient of inbreeding 2.15%.

Before 15 Feb 1404 [his illegitimate brother-in-law] Thomas Beaufort 1st Duke Exeter (age 27) and Margaret Neville Countess Dorest (age 20) were married. He the illegitmate son of [his father-in-law] John of Gaunt 1st Duke Lancaster and Katherine Roet Duchess Lancaster. He a grandson of King Edward III of England.

On 06 Mar 1405 [his son] John II King Castile was born to Henry III King Castile (age 25) and [his wife] Catherine of Lancaster Queen Consort Castile (age 31). He a great grandson of King Edward III of England. Coefficient of inbreeding 2.15%.

On 26 Nov 1405 Thomas Fitzalan 10th Earl of Surrey 12th Earl of Arundel (age 24) and Beatrice Aviz Duchess Exeter (age 23) were married. [his brother-in-law] King Henry IV of England (age 38) and Joanna of Navarre Queen Consort England (age 35) were present at their wedding feast. She the illegitmate daughter of King John I of Portugal (age 53) and Ines Peres. He the son of Richard Fitzalan 9th Earl of Surrey 11th Earl of Arundel and Elizabeth Bohun Countess Arundel and Surrey. He a great x 2 grandson of King Edward I of England.

On 02 Jun 1418 [his former wife] Catherine of Lancaster Queen Consort Castile (age 45) died at Valladolid [Map]. She was buried at Capilla de los Reyes Nuevos, Cathedral of Toledo.