Louis Philogène Brulart was born 12 May 1702, only son of Carloman Philogène Brulart, Comte de Sillery (ca. 1663–1727) and his wife Mary-Louise Bigot (1662-1746); he also had a sister, Marie (1707-1771). His father commanded the Regiment de Conti but his career ended after he was badly wounded at Landen in 1693.