His sister Amable married Gilbert Antoine des Aix, seigneur de Veygoux, and was mother to the famous General Desaix, who died at the Battle of Marengo in 1800.
On 25 November 1755 he was married to Marie-Louise O'Murphy, "la belle Morphyse", who had been one of King Louis XV's mistresses.
Upon her unwise attempt to take the place of longtime favorite Madame de Pompadour as maitresse-en-titre, Louis XV sent O'Murphy away, gave her a false identity as "Marie-Louise Morphy de Boisfailly", daughter of an Irish gentleman, and had his agents quickly find her a suitable husband.
Beaufranchet was selected for his aristocratic family, youth and handsomeness, respectable military career, and relative lack of money.
He was survived by his wife; their daughter, Louise; and their son, Louis Charles Antoine de Beaufranchet, who was born seventeen days after his father's death.