Alan I was the eldest son of Count Henry of Trégor from the latter’s marriage to Mathilde, daughter of Count John I of Vendôme .
Around 1183 he succeeded his deceased father as lord of Goëlo and Avaugour. Two years later, at an assembly of Breton nobles, he honored King Philip II of France as his liege lord.
Four years later, in 1189, he was among the nobles who opposed the claims made by King Richard I of England to the regency of the young duke Arthur I of Brittany .
(From Here) Between 1184 and 1189 he founded a monastery near Paimpol , on the Île Saint-Riom , which was intended for the canons at Saint-Victor Abbey in Paris .
In 1200, this monastery was taken over by the Premonstratensians of the Abbey of La Lucerne and was given a new name, the Abbey of Beaufort (To Here)
In 1206 he inherited from his childless cousin Godfrey III the County of Penthièvre, as did the latter’s claims to the Duchy of Brittany .
This legacy was confirmed by the remaining heirs of Godfrey and Philip II of France. Since Guy de Thouars , the real duke of Brittany, feared a conflict with Alan, he granted him the northern part of Brittany, more specifically the areas comprising the dioceses of Saint-Malo , Dol-de-Bretagne , Saint-Brieuc and Saint-Pol -de-Léon.