Evidence of a fractured leadership appeared in letters from Pope John XIII to Brittany who addressed "Juhel Béranger and his son Conan, as well as Hoël and his brother Guérech.
"[b] In 975, Hoël I entered into a conflict with Conan I Le Tort, the Count of Rennes, son of Juhel Béranger and the eventual Duke of Brittany after the rule of Hoël and his brother Guérech.
A battle ensued at Conquereuil where Geoffrey defeated Conan I, although the military result of the battle was indecisive, as different results are recorded in the Chronicles of Nantes and Mont St Michel.
[d] In 981, Hoël I worked to have his brother Guérech elected Bishop of Nantes to replace Gauthier I who had died.
He had at least two known children: In 981, during Guérech's visit to the Metropolitan of Tours, who controlled all bishops in Brittany, Hoël I was assassinated by Galuron under the orders of Conan I. Guérech left his bishopric of Nantes before being consecrated Bishop and was elected Count of Nantes.