 He was born on July 20, 1862, in Paris to former U.S. Representative George Eustis Jr. (1828–1872) and Louise Morris "Lulie" (née Corcoran) Eustis (1838–1867), who married in April 1859.His brother was George Peabody Eustis and his younger sister was Louise Marie Eustis, who married polo player Thomas Hitchcock Sr.He was a grandson of Clarisse (née Allain) Eustis and George Eustis Sr., Chief Justice of the Louisiana Supreme Court.