Ermengarde-Blanche was the daughter of Count Fulk III of Anjou and Hildegarde. She was involved in two marriage alliances that greatly benefited her father and brother as counts of Anjou. She was first contracted to marry Geoffrey II, Count of Gâtinais, called "Ferréol", who was also lord of Château-Landon. It was important marriage to return Château-Landon to the counts of Anjou. It took between twelve and eighteen months to arrange the marriage. Meanwhile Fulk paid a great deal of attention to Château-Landon. He and his wife, Hildegarde, founded the abbey of Le Ronceray. Originally a church dedicated to St. Mary, Hildegard was very active in its rebuilding into an abbey. They gave the abbey many gifts including the forest of Lattay. They gave more gifts to this abbey than any other church or religious house. Her two sons of this marriage, Geoffrey III and Fulk both became counts of Anjou after her brother Geoffrey II Martel. Among her descendants are the Plantagenet (or Angevin) kings of England.