Between Feb 1171 and Apr 1175 [her step-father] Humphrey Bohun (age 31) and [her mother] Margaret Dunkeld Duchess Brittany (age 26) were married. She the daughter of Henry Dunkeld 3rd Earl Huntingdon 1st Earl of Northumbria and Ada Warenne Countess Huntingdon and Northumbria (age 51).

On 27 Aug 1172 [her future brother-in-law] Henry the Young King (age 17) and Margaret Capet (age 15) were married at Winchester Cathedral [Map]. Margaret's dowry included the Vexin; the border between France and Normandy. On the same day they were both crowned by Rotrou Newburgh Archbishop Rouen. She the daughter of Louis VII King Franks (age 52) and Constance of Castile. He the son of King Henry "Curtmantle" II of England (age 39) and Eleanor of Aquitaine Queen Consort Franks and England (age 50). They were half 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.

In 1188 Ranulf de Blondeville Gernon 6th Earl Chester 1st Earl Lincoln (age 18) and Constance Penthièvre Duchess Brittany (age 27) were married. She by marriage Countess Chester. She the daughter of Conan "The Young" Penthièvre IV Duke Brittany and Margaret Dunkeld Duchess Brittany (age 43). He the son of Hugh de Kevelioc Gernon 5th Earl Chester and Bertrade Montfort Countess Chester. They were half third cousins. He a great x 2 grandson of King Henry I "Beauclerc" England. She a great x 2 granddaughter of King Henry I "Beauclerc" England.

Before 1200 Guy Thouars (age 60) and Constance Penthièvre Duchess Brittany (age 38) were married. The difference in their ages was 21 years. She the daughter of Conan "The Young" Penthièvre IV Duke Brittany and Margaret Dunkeld Duchess Brittany (age 54). She a great x 2 granddaughter of King Henry I "Beauclerc" England.

Aimery Thouars VII Viscount Thouars and Cecile or Sybil Laval Viscountess Thouars were married. She a granddaughter of King Henry I "Beauclerc" England.

William de Hertburn Fitzpatrick and [her mother] Margaret Dunkeld Duchess Brittany were married. She the daughter of Henry Dunkeld 3rd Earl Huntingdon 1st Earl of Northumbria and Ada Warenne Countess Huntingdon and Northumbria.

[her father] Conan "The Young" Penthièvre IV Duke Brittany and [her mother] 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.