He was the second son of Bouchard III of Montmorency, and his elder brother was Thibaud, Constable of France.
Hervé received the seigneury of Marly as an appanage.
He is first mentioned in a charter issued by King Philip I to the priory of Saint-Martin-des-Champes in 1067.
[2] Apart from his signature on documents issued by the Royal Chancellory, little is known about him, although André Duchesne described Hervé as "one of the most secular princes of the Kingdom".
[3] After the death of his childless elder brother, he inherited the seigneury of Montmorency and reunited the family holdings.