He was the son of M. de Saint-Aignan, who with honour and valour was truly romantic in gallantry, in belles-lettres, and in arms. He was Captain of the Guards of Gaston, and at the end of 1649 bought of the Duc de Liancourt the post of first-gentleman of the King's chamber. He commanded afterwards in Berry against the party of M. le Prince, and served elsewhere subsequently. In 1661 he was made Chevalier of the Order, and in 1661 Duke and Peer. His first wife he lost in 1679. At the end of a year he married one of her chambermaids, who had been first of all engaged to take care of her dogs. She was so modest, and he so shamefaced, that in despite of repeated pressing on the part of the King, she could not be induced to take her tabouret. She lived in much retirement, and had so many virtues that she made herself respected all her life, which was long. M. de Beauvilliers was one of the children of the first marriage. I know not what care M. and Madame de Saint-Aignan took of the others, but they left him, until he was six or seven years of age, to the mercy of their lodge-keeper. Then he was confided to the care of a canon of Notre Dame de Clery. The household of the canon consisted of one maid-servant, with whom the little boy slept; and they continued to sleep together until he was fourteen or fifteen years old, without either of them thinking of evil, or the canon remarking that the lad was growing into a man. The death of his eldest brother called M. de Beauvilliers home. He entered the army, served with distinction at the head of is regiment of cavalry, and was brigadier.