His elder brother Aymar Hennequin was also a bishop and they both supported the Catholic League.
He was the sixth son of Renée Nicolaï and her husband Dreux Hennequin († 1550), lord of Assy, president of the chambre des comptes of Paris.
He was initially a canon of Notre Dame de Paris and was made bishop of Soissons in 1587.
[1] In 1612 he gained permission for his nephew Dreux Hennequin de Villenoxe († 1651) to be made coadjutor with right of succession and in 1618 he resigned the commendatory of abbaye Notre-Dame de Bernay in his favour (he had inherited it on Aymar's death in 1596).
When Jérôme died in 1619, however, Dreux renounced these titles in favour of his cousin Charles de Hacqueville, another of Jérôme's nephews via his mother Anne Hennequin, who had Charles confirmed as bishop by pope Paul V on 12 August 1619.