Emily Upjohn is out of Hidden Brief (Barathea), who was third in the Listed Prix Petite Etoile at Deauville. She is one of six foals aged three and over out of Hidden Brief, who had been the dam of two minor winners before her. Hidden Brief is a full-sister to Hazarista, winner of the Gr.3 Blue Wind S. and third in both the Gr.1 Irish Oaks and the Gr.1 Yorkshire Oaks.

Second dam Hazaradjat (Darshaan) was a winner and is a half-sister to Hittite Glory (Habitat), a Group 1 winner at two and later a sire. Besides Hazarista she bred Hazariya (Xaar), a Group 3 winner over seven furlongs and dam of the dual Classic winner and sire Harzand (Sea The Stars), the Group 3 winner Harasiya (Pivotal), also third in the Gr.1 Moyglare Stud S., and the Listed winners Haripour (Shamardal) and Hazarafa (Daylami), the latter winner of the Listed Finale S. and dam of Hazapour (Shamardal), winner of the Gr.3 Derrinstown Stud Derby Trial and the Gr.3 Amethyst S. Also from this branch are Seal Of Approval (Authorized), winner of the Gr.1 British Champions Fillies & Mares S., Hurricane Lane (Frankel), winner of the Gr.1 Irish Derby, the Gr.1 St Leger and the Gr.1 Grand Prix de Paris, and the group winners Hunaina (Tamayuz), Swashbuckling (Raven's Pass), who raced as Big Duke in Australia, Hamairi, Vadream (Brazen Beau) and Hamariyna (Sea The Moon).

Third dam Hazy Idea (Hethersett), a Listed winner, had 11 winners from 13 foals, among them Hittite Glory and two Listed winners by Red God and Crepello.

Hidden Brief has the unraced 2-year-old filly Hidden Jewel (Cappella Sansevero).