Weis' "Ancestral Roots. . ." (39:24) calls him Count of Cornouille and jure uxoris Duke of Brittany 1066. Also mentioned (119:24). Per Galliou and Jones' "The Bretons", The middle decades of the 11th century were extremely turbulent in all western French principalities. The minorities of WILLIAM THE CONQUERER in Normandy and Conan II [ALAIN III's son/ Hoel'sbrother-in-law) in Brittany and the aggressive policies of Geoffrey Martel, Count of Anjou [son of FULK NERRA], followed by a succession crisis on his death, stirred lesser figures, notably ambitious castellan lords, to assert their independence of central authority. This was seriously weakened in Brittany, as elsewhere, by civil war, especially that between Conan II and his uncle and former guardian, EUDES. WILLIAM THE CONQUERER attracted several of the Breton lords from the northeast of the duchy into his service. In 1664 WILLIAM even campaigned in Brittany in behalf of Rivallon of Cambour and against Conan II. Conan was killed in 1066 while campaigning against the Angevins. He left no obvious heir and a succession crisis ensued. Hoel claimed the Duchy by right of his marriage to ALAIN III's daughter and Conan's sister, HAWISE, and held it until his own death in 1084, passing it on to his son, ALAIN IV FERGANT.