Guéthénoc, vicomte du Porhoët

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Guéthénoc de Thro en de Chateau Tro en Porhoët (Porhoet), vicomte du Porhoët

Also Known As: "Guezenoc ou Guéthénoc"
Birthplace: La Trinité-Porhoët, Bretagne, France
Death: Died in Puy-de-Dôme, Auvergne, France
Place of Burial: Redon - Abbaye, 35, Brittany, France
Immediate Family:

Son of Judicaël, comte de Porhoët and Rantlina de Vitre
Husband of Allarum de Cornouaille
Father of Josselin I de Thro en Porhoët, vicomte de Bretagne et de Rennes; Mainguy De ROHAN; Tutgual de ROHAN; N.N. de Porhoët and Eudes la Zouche
Half brother of Martin d'Acigné; Raentlina de Bretagne and Roianteline de DOL

Occupation: Vicomte, de Porhoët, de Châteautro-en-Penhoët, de Rennes, Vicomte de Chateaudro en Porhoët-Comte de Poher, He became Vicomte, and in about 1008 he moved to La Trinite, in Porhoet, Morbihan, Brittany. There he built Castle Josselin,
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About Guéthénoc, vicomte du Porhoët

Stuart Baldwin Website, writes:

Juthael, count of Porhoët (existence uncertain)

The Breton genealogist du Paz is the evident source (followed by numerous secondary sources) for the statement that Conan had a son Juthael, count of Porhoët, the claimed father of viscount Guethenoc, who witnessed a charter of duke Geoffroy I (d. 1008) [Cart. Redon, 247]. In a discussion of the origin of the counts of Porhoët [Morice (1750): 1: 975-9 (Note XLV)], Morice cites "Hist. Mss. des Comtes de Porhoet" by du Paz as the source. However, there does not appear to be any confirmation of even the existence of Juthael, count of Porhoët, and the well documented genealogy of the viscounts and counts of Porhoët begins with Guethenoc.ët

From Wikipedia, the free encyclopedia

The noble Breton family line of Porhoët is represented in modern times by the Franco-Breton House of Rohan. Josselin Castle and the River Oust

The first recognised vicomte de Porhoet was Guithenoc (abt. 990-1040CE), was born in Guilliers. He married Allurum (994-?) of Guilliers. He became Vicomte, and in about 1008 he moved to La Trinite, in Porhoet. Both Guilliers and Porhoet are located in the modern day French Departement of Morbihan in the province of Brittany.

In Porhoët Guithenoc built Josselin Castle, which he named for his son, Josselin (1020–1074). It is still owned by the descendants of Porhoet and is the longest continuously held private estate in the world.

Vicomte Josselin de Porhoet had three sons with the surname Rohan: Mainguy De Rohan, Jostho de Rohan, and Roger de Rohan. He had a fourth son, the third vicomte de Porhoet, Eudo I de Porhoet (1049-?).

Eudo (or Eudes) I married Anne de Leon (1065-?). They had two children, Vicomte Geoffrey de Porhoet (1092–1141) and Alain I de Rohan

Geoffrey is said to have married Hawisa Fergant of Brittany (abt. 1105-?). They had two sons, one of which was as Odo II or Odo, Viscount of Porhoet (1122-?).

Franco-Breton House of Rohan

Alain le Noir was the 1st Viscount de Rohan. He was the third son of Eudes I de Porhoet and his wife Emma de Léon (the daughter of Guyomarch II, Viscount de Léon). The name Rohan comes from the name of the castle he built, and passed on to his descendants, on the shores of the Oust.

His son, Eudes, married Bertha, the daughter of Conan III and Empress Matilda. They had no descendants.

Viscount of Porhoet as Duke of Brittany

Eudes II of Porhoet, known also as Odo II is a notable figure in the history of the Duchy of Brittany.

Odo II married into the ruling duchy of Brittany through his first marriage to Bertha (b.1114-?). This was Bertha's second marriage. She was the daughter of Conan III, Duke of Brittany. Upon Bertha's death, Odo II served as Regent to Bertha's son Conan IV of Penthièvre. Bertha and Odo II had three children permitting the Porhoet line to continue. Bertha's sister Constance (1118-?) was next in line to the duchy (after Bertha); she married Alan, younger brother to Odo II, thus cementing Porhoet claims to Brittany.

When Bertha died, Odo II tried to deny Conan IV his inheritance and usurp the rule of Brittany. He formed an alliance with Hoel, Count of Nantes, Conan III's disinherited son.[a] In order to counter Odo II, Henry II of England invaded Brittany. [b] In 1516 Odo was deposed by his step son and imprisoned by Conan IV's ally Raoul de Fougeres. Henry II raised Josselin Castle.

Odo II possibly had a second marriage with Jeanne/Eléonore de Léon, daughter of Guiomar III, Vicomte de Léon. They had two, and possibly three, children.

The Vicomtes and Counts of Porhoët

  • Guithenoc (990 - 1040) - becomes Vicomte;
  • Josselin - Vicomte de Porhoet - son of Vicomte Guithenoc
  • Odo[c] I, Vicomte de Porhoët- son of Vicomte Josselin
  • Geoffrey, Victome de Porhoët - son of Odo I, married Hawise Fergant of Brittany
  • Odo II - husband of Bertha and so son-in-law of Conan III, Duke of Brittany; contested the Ducal Crown of Brittany
  • Odo III, Comte de Porhoët - son of Odo III
  • Yolande de Dreux (1218-1272), Comtesse de Porhoët [d]
  • Alan, [e] - son of Odo III; flees to England
  • Alan de Porhoët - younger brother of Odo II, husband to Constance of Brittany, the younger sister of Bertha
  • Alan - Vicomte de Rohan; son of Odo I and founder of the House of Rohan


  1. ^ In order to consolidate his power, King Henry II of England (5 March 1133- 6 July 1189) had planned to replace Duke Conan III of Brittany with someone from his immediate family. He had promised his younger brother Geoffrey, of the house of Plantegenet, this duchy if he succeeded to the throne of England. To this end, he had Conan III disinherit his son Hoel III, claiming him as illegitimate. (Hoel III's mother, the Duchess, Maude, was a daughter and illegitimate heir to Henry I of England). This meant that Bertha, who was the next in line to the duchy of Brittany, became the legitimate heir to the estate of Conan III.
  2. ^ Henry II faced anarchy on many fronts; he was in the midst of the "Nineteen Year Winter." His younger brother Geoffrey, to whom he had promised the duchy, also contested the throne. As a result of the invasion of Brittany, the Porhoet family eventually recognised Henry II as King.
  3. ^ Odo, in French, is Eudes.
  4. ^ Countess of Porhoët suo jure; her father was Pierre Mauclerc
  5. ^ In an earlier edition of this article he is listed as the 1st Baron Zouche. This claim is under review.


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Après s'être installé vers l'an 1000 au château Tro à Guiliers, Guéthénoc construisit un château sur les rives de l'Oust, en lisière de la grande forêt de Lannouée. Son fils donne son nom au château "Castelum Goscelini" (Josselin).

(P. André - dict. d'Histoire de Bretagne)

After moving around the year 1000 the castle to Guiliers Tro, Guéthenoc built a castle on the banks of the River Oust, on the edge of the great forest of Lannouée. His son gave his name to the castle "Castelum Goscelini" (Josselin).


Guethenoc's parentage is undocumented, but probable.

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Guéthénoc, vicomte du Porhoët's Timeline

La Trinité-Porhoët, Bretagne, France
Age 7
Guilliers, Morbihan, France
Age 11
Guilliers, Morbihan, France
Age 12
Age 22
Age 38
Puy-de-Dôme, Auvergne, France
Age 38
Redon - Abbaye, 35, Brittany, France