In 1087 Alan Canhiart IV Duke Brittany (age 24) and Constance Normandy Duchess Brittany (age 30) were married. She by marriage Duchess Brittany. She the daughter of King William "Conqueror" I of England (age 59) and Matilda Flanders Queen Consort England. They were third cousins.

In 1093 Alan Canhiart IV Duke Brittany (age 30) and Ermengarde Anjou Duchess Brittany and Aquitaine (age 25) were married. She by marriage Duchess Brittany. She the daughter of Fulk "Réchin" Anjou 4th Count Anjou (age 50) and Hildegarde Beaugency Countess Anjou (age 49). They were third cousin once removed.

Before 1113 Conan "Fat" Canhiart III Duke Brittany (age 17) and Matilda Fitzroy Duchess Brittany were married. She by marriage Duchess Brittany. She the illegitmate daughter of King Henry I "Beauclerc" England (age 44). He the son of Alan Canhiart IV Duke Brittany (age 49) and Ermengarde Anjou Duchess Brittany and Aquitaine (age 44). They were fourth cousins.

In Jul 1181 Geoffrey Plantagenet 2nd Duke Brittany (age 22) and Constance Penthièvre Duchess Brittany (age 20) were married. She by marriage Duchess Brittany. He by marriage Duke Brittany. She the daughter of Conan "The Young" Penthièvre IV Duke Brittany and Margaret Dunkeld Duchess Brittany (age 36). He the son of King Henry "Curtmantle" II of England (age 48) and Eleanor of Aquitaine Queen Consort Franks and England (age 59). They were half second cousin once removed. She a great x 2 granddaughter of King Henry I "Beauclerc" England.

Francis Montfort I Duke Brittany and Isabella Stewart Duchess Brittany were married. She by marriage Duchess Brittany. She the daughter of King James I of Scotland and Joan Beaufort Queen Consort Scotland. He a great x 4 grandson of King Henry III of England. She a great x 2 granddaughter of King Edward III of England.

Francis Montfort I Duke Brittany and Yolande Valois Anjou Duchess Brabant Duchess Brittany were married. She by marriage Duchess Brittany. She the daughter of King Louis of Naples and Yolanda Barcelona Queen Consort Naples. They were second cousin once removed. He a great x 4 grandson of King Henry III of England. She a great x 5 granddaughter of King Henry III of England.

Conan "The Young" Penthièvre IV Duke Brittany and Margaret Dunkeld Duchess Brittany were married. She by marriage Duchess Brittany. She the daughter of Henry Dunkeld 3rd Earl Huntingdon 1st Earl of Northumbria and Ada Warenne Countess Huntingdon and Northumbria. He the son of Alan "Black" Penthièvre 1st Earl Richmond and Bertha Canhiart I Duchess Brittany. They were half fourth cousins. He a great grandson of King Henry I "Beauclerc" England.