In 1275 [his father] Arthur Capet Duke Brittany (age 13) and [his mother] Marie Limoges Duchess Brittany were married. She by marriage Duchess Brittany 1221 Dreux. He the son of John Capet II Duke Brittany (age 36) and Beatrice Plantagenet (age 32). They were third cousins. He a grandson of King Henry III of England.

On 01 Dec 1291 James "The Just" II King Aragon (age 24) and [his future wife] Isabella Ivrea Queen Consort Aragon (age 8) were married. She by marriage Queen Consort Aragon. She the daughter of Sancho IV King Castile IV King Leon (age 33) and Maria Molina Queen Consort Castile Queen Consort Leon. He the son of Peter III King Aragon and Constance Hohenstaufen Queen Consort Aragon (age 42). They were first cousin once removed. She a great x 4 granddaughter of King Henry "Curtmantle" II of England.

In or before 1295 [his father] Arthur Capet Duke Brittany (age 33) and [his step-mother] Yolande Capet Duchess Brittany (age 33) were married. She by marriage Duchess Brittany 1221 Dreux. She the daughter of Robert Capet IV Count Dreux and Beatrice Montfort Countess Dreux (age 46). He the son of John Capet II Duke Brittany (age 55) and Beatrice Plantagenet. They were third cousins. He a grandson of King Henry III of England. She a great x 5 granddaughter of King Henry I "Beauclerc" England.

In 1297 John Capet III Duke Brittany (age 10) and Isabelle Valois Duchess Brittany (age 5) were married. She by marriage Duchess Brittany 1221 Dreux. She the daughter of Charles Valois I Count Valois (age 26) and Margaret Capet Countess Valois (age 24). They were third cousins. He a great grandson of King Henry III of England. She a great x 4 granddaughter of King Henry "Curtmantle" II of England.

In 1310 John Capet III Duke Brittany (age 23) and Isabella Ivrea Queen Consort Aragon (age 27) were married. She by marriage Duchess Brittany 1221 Dreux. She the daughter of Sancho IV King Castile IV King Leon and Maria Molina Queen Consort Castile Queen Consort Leon. He a great grandson of King Henry III of England. She a great x 4 granddaughter of King Henry "Curtmantle" II of England.

In 1329 John Capet III Duke Brittany (age 42) and Joan Savoy Duchess Brittany (age 19) were married. She by marriage Duchess Brittany 1221 Dreux. The difference in their ages was 23 years. She the daughter of Edward "Liberal" Savoy Count Savoy (age 45) and Blanche Burgundy Countess Savoy (age 41). They were second cousins. He a great grandson of King Henry III of England. She a great x 4 granddaughter of King Henry "Curtmantle" II of England.

Peter Ivrea and Maria Barcelona were married. She the daughter of James "The Just" II King Aragon and Blanche Capet Queen Consort Aragon. He the son of Sancho IV King Castile IV King Leon and Maria Molina Queen Consort Castile Queen Consort Leon. They were second cousins. He a great x 4 grandson of King Henry "Curtmantle" II of England. She a great x 4 granddaughter of King Henry "Curtmantle" II of England.