Biography of Constance of Castile Duchess of Lancaster 1354-1394
Paternal Family Tree: Ivrea
Maternal Family Tree: María González Henestrosa Lady Villagera 1356
1348 Black Death Plague Outbreak
1369 Death of Peter I King Castile
On 26 Mar 1350 [her grandfather] Alfonso "Avenger" XI King Castile (age 38) died of plague. His son [her father] Peter "Cruel" I King Castile (age 15) succeeded I King Castile.
Around Jul 1353 [her father] Peter "Cruel" I King Castile (age 18) and Blanche Bourbon Queen Consort Castile (age 14) were married. She by marriage Queen Consort Castile. She the daughter of Peter Bourbon Duke Bourbon (age 42) and Isabella Valois Duchess Bourbon (age 40). He the son of Alfonso "Avenger" XI King Castile and Maria Burgundy Queen Consort Castile (age 40). They were third cousin once removed. He a great x 5 grandson of King Henry "Curtmantle" II of England. She a great x 3 granddaughter of King Henry III of England. 
In 1354 Constance of Castile Duchess of Lancaster was born illegitimately to Peter "Cruel" I King Castile (age 19) and Maria Padilla (age 20).
In Jul 1361 [her mother] Maria Padilla (age 27) died at Seville.
On 03 Apr 1367 the forces of [her father] Peter "Cruel" I King Castile (age 32) commanded by Edward "Black Prince" (age 36) defeated the army of [her uncle] Henry "Fratricide" II King Castile (age 33) at the Battle of Nájera at Nájera. The English forces included John of Gaunt 1st Duke Lancaster (age 27), William Scrope, Peter Courtenay (age 21), John Devereux 1st Baron Devereux (age 30), John Savile of Shelley and Golcar (age 42), Bernard Brocas (age 37) and Thomas Banastre (age 33).
The forces of Henry "Fratricide" II King Castile (age 33) included Bertrand Geusclin (age 47). The battle achieved little since Bertrand Geusclin (age 47) escaped.
John Ferrers 4th Baron Ferrers of Chartley (age 36) was killed. His son Robert Ferrers 5th Baron Ferrers of Chartley (age 9) succeeded 5th Baron Ferrers of Chartley. Margaret Despencer Baroness Ferrers of Chartley by marriage Baroness Ferrers of Chartley.
Edward "Black Prince" (age 36) thereafter returned home, taking Peter's daughters Constance (age 13) and [her illegitimate sister] Isabella (age 12) as hostages to ensure Peter would pay the money owed to Edward. Constance (age 13) married John of Gaunt 1st Duke Lancaster (age 27), Isabella (age 12) married Edmund of Langley 1st Duke York (age 25).
On 23 Mar 1369 [her father] Peter "Cruel" I King Castile (age 34) was murdered by his half-brother [her uncle] Henry "Fratricide" II King Castile (age 35) outside the wall of the castle of Montiel, La Mancha. His half brother Henry "Fratricide" II King Castile (age 35) succeeded II King Castile.
On 21 Sep 1371 John of Gaunt 1st Duke Lancaster (age 31) and Constance of Castile Duchess of Lancaster (age 17) were married at Roquefort, Landes. She by marriage Duchess Lancaster. His younger brother Edmund of Langley 1st Duke York (age 30) married Constance's sister in July 1372. An example of Marriage of Two Sets of Siblings. She the illegitmate daughter of Peter "Cruel" I King Castile and Maria Padilla. He the son of King Edward III of England (age 58) and Philippa of Hainault Queen Consort England.
After 21 Sep 1371 [her illegitimate sister] Isabella of Castile Duchess York (age 16) accompanied her sister Constance of Castile Duchess of Lancaster (age 17) to England after her marriage to John of Gaunt 1st Duke Lancaster (age 31).
On 09 Feb 1372 Constance of Castile Duchess of Lancaster (age 18), the wife of John of Gaunt 1st Duke Lancaster (age 31) made a ceremonial entryin London.
On 11 Jul 1372 Edmund of Langley 1st Duke York (age 31) and [her illegitimate sister] Isabella of Castile Duchess York (age 17) were married at Wallingford, Oxfordshire [Map]. She by marriage Countess Cambridge. She being the younger sister of Constance (age 18) who had married Edmund's older brother John of Gaunt 1st Duke Lancaster (age 32) a year before. An example of Marriage of Two Sets of Siblings. She the illegitmate daughter of Peter "Cruel" I King Castile and Maria Padilla. He the son of King Edward III of England (age 59) and Philippa of Hainault Queen Consort England.
Letters. 07 Aug 1372. 1372 the earliest date based on her marriage in 1371. Letter XXV. Constance (age 18), Wife of John of Gaunt Duke of Lancaster, to the Chancellor of England.
From the Queen of Castile and Leon, Duchess of Lancaster.
Honoured sir.
We pray you lovingly that you will grant your letters for Friar Alvare, the bearer of these, to the prior of the friars-preachers of Oxford, that the said friar may be received there to be a student in the university of the said city, for love of me. And may our Lord ever have you, honoured sir, in his holy keeping.
On 31 Mar 1373 [her daughter] Catherine of Lancaster Queen Consort Castile was born to John of Gaunt 1st Duke Lancaster (age 33) and Constance of Castile Duchess of Lancaster (age 19) at Hertford Castle [Map]. She a granddaughter of King Edward III of England.
In 1374 [her son] John Lancaster was born to John of Gaunt 1st Duke Lancaster (age 33) and Constance of Castile Duchess of Lancaster (age 20). He a grandson of King Edward III of England.
In 1375 [her son] John Lancaster (age 1) died.
Before 17 Sep 1388 [her son-in-law] Henry III King Castile (age 8) and [her daughter] Catherine of Lancaster Queen Consort Castile (age 15) were married at Palencia Cathedral. 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. 
On 23 Dec 1392 [her illegitimate sister] Isabella of Castile Duchess York (age 37) died. She the wife of Edmund of Langley 1st Duke York (age 51). Isabella had travelled to England with her sister Constance of Castile Duchess of Lancaster (age 38) who had married Edmund's elder brother John of Gaunt 1st Duke Lancaster (age 52). Isabella and Edmund's marriage was not, apparently, a happy one. She is known to have had an affair with John Holland 1st Duke Exeter (age 40) who may have been the father of Richard of Conisbrough 1st Earl Cambridge (age 7) progenitor of the House of York.
On 24 Mar 1394 Constance of Castile Duchess of Lancaster (age 40) died at Leicester Castle [Map]. She was buried at Church of the Annunciation of our Lady of the Newark [Map].
On 16 Dec 1485 Catherine of Aragon was born to Ferdinand II King Aragon (age 33) and Isabella Queen Castile (age 34). She was possibly named after her Great Grandmother [her daughter] Catherine of Lancaster Queen Consort Castile daughter of John of Gaunt 1st Duke Lancaster and Constance of Castile Duchess of Lancaster. She a great x 3 granddaughter of King Edward III of England. Coefficient of inbreeding 3.23%.
Kings Wessex: Great x 11 Grand Daughter of King Edmund "Ironside" I of England
Kings England: Great x 6 Grand Daughter of King Henry "Curtmantle" II of England
Kings Scotland: Great x 9 Grand Daughter of Malcolm III King Scotland
Kings Franks: Great x 17 Grand Daughter of Louis "Pious" King Aquitaine I King Franks
Kings France: Great x 10 Grand Daughter of Robert "Pious" II King France
Great x 4 Grandfather: Ferdinand III King Castile III King Leon Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Alfonso X King Castile X King Leon 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Elisabeth Hohenstaufen Queen Consort Castile Queen Consort Leon
Great x 2 Grandfather: Sancho IV King Castile IV King Leon 3 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: James I King Aragon
Great x 3 Grandmother: Violante Barcelona Queen Consort Castile Queen Consort Leon
Great x 4 Grandmother: Violant Árpád Queen Consort Aragon
Great x 1 Grandfather: Ferdinand IV King Castile IV King Leon 4 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Maria Molina Queen Consort Castile Queen Consort Leon
GrandFather: Alfonso "Avenger" XI King Castile 4 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Alfonso "Fat" II King Portugal
Great x 3 Grandfather: Alfonso III King Portugal Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Urraca Ivrea Queen Consort Portugal Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Denis I King Portugal 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Alfonso X King Castile X King Leon 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Beatrice Queen Consort Portugal 3 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Mayor Guillén de Guzmán
Great x 1 Grandmother: Constance Burgundy Queen Consort Castile Queen Consort Leon 3 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandfather: James I King Aragon
Great x 3 Grandfather: Peter III King Aragon
Great x 4 Grandmother: Violant Árpád Queen Consort Aragon
Great x 2 Grandmother: Elisabeth Barcelona Queen Consort Portugal 6 x Great Grand Daughter of King William "Conqueror" I of England
Great x 4 Grandfather: Manfred King Sicily
Great x 3 Grandmother: Constance Hohenstaufen Queen Consort Aragon 5 x Great Grand Daughter of King William "Conqueror" I of England
Great x 4 Grandmother: Beatrice Savoy Marchioness of Saluzzo 4 x Great Grand Daughter of King William "Conqueror" I of England
Father: Peter "Cruel" I King Castile 5 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Alfonso "Fat" II King Portugal
Great x 3 Grandfather: Alfonso III King Portugal Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Urraca Ivrea Queen Consort Portugal Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Denis I King Portugal 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Alfonso X King Castile X King Leon 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandmother: Beatrice Queen Consort Portugal 3 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Mayor Guillén de Guzmán
Great x 1 Grandfather: Alfonso "Brave" IV King Portugal 3 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: James I King Aragon
Great x 3 Grandfather: Peter III King Aragon
Great x 4 Grandmother: Violant Árpád Queen Consort Aragon
Great x 2 Grandmother: Elisabeth Barcelona Queen Consort Portugal 6 x Great Grand Daughter of King William "Conqueror" I of England
Great x 4 Grandfather: Manfred King Sicily
Great x 3 Grandmother: Constance Hohenstaufen Queen Consort Aragon 5 x Great Grand Daughter of King William "Conqueror" I of England
Great x 4 Grandmother: Beatrice Savoy Marchioness of Saluzzo 4 x Great Grand Daughter of King William "Conqueror" I of England
GrandMother: Maria Burgundy Queen Consort Castile 4 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 4 Grandfather: Ferdinand III King Castile III King Leon Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Alfonso X King Castile X King Leon 2 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandmother: Elisabeth Hohenstaufen Queen Consort Castile Queen Consort Leon
Great x 2 Grandfather: Sancho IV King Castile IV King Leon 3 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 4 Grandfather: James I King Aragon
Great x 3 Grandmother: Violante Barcelona Queen Consort Castile Queen Consort Leon
Great x 4 Grandmother: Violant Árpád Queen Consort Aragon
Great x 1 Grandmother: Beatrice Ivrea Queen Consort Portugal 4 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 2 Grandmother: Maria Molina Queen Consort Castile Queen Consort Leon
Constance of Castile Duchess of Lancaster 6 x Great Grand Daughter of King Henry "Curtmantle" II of England
Great x 1 Grandfather: Garcia Padilla
GrandFather: Juan García Padilla 1st Lord Villagera
Mother: Maria Padilla
Great x 1 Grandfather: Fernán González Henestrosa
GrandMother: María González Henestrosa Lady Villagera