When Enguerrand abducted and married his second wife, Sibyl of Château-Porcien, she was still married to Godfrey of Lorraine, while he was absent and at war. Thus, Enguerrand and Godfrey became bitter enemies, fighting each other in a private war. Thomas of Marle hated his father and joined his enemies. Still, in 1095 they both took part in the First Crusade.
Thomas even cut the throat of a relative, archdeacon Walter of Laon. He supported the citizens of Laon in their rising of 1112, and sheltered its leaders. As a result Thomas was excommunicted in 1114, and condemned in the Royal Court of France, but continued with his deplorable activities.
In 1102 Thomas had married Ida of Hainault and they subsequently had 2 daughters. After Ida's death he married Melisende of Crécy in 1108, and had 2 sons and 2 more daughters. Thomas succeeded his father upon Enguerrand's death in 1116.
In 1130, while King Louis VI was hampered by obesity, his relative Raoul of Vermandois* organized an expedition against Thomas of Marle. At Coucy Ralph's men caught him, and Raoul pierced him with his sword - before handing him over to the French King. Thomas made a long confession, was imprisoned, and died soon afterwards in prison.
Peace was finally achieved when Thomas' son, Enguerrand II, married Agnès de Beaugency, a niece of Raoul of Vermandois. It was Enguerrand VII de Coucy (1340-97) who married Princess Isabella (1332-82), daughter of English King Edward III.