Soul Sister is the sixth foal out of Dream Peace (Dansili), a Group winner in France who took the Gr.2 Prix de la Nonette and was five times placed at Group 1 level, including at Grade 1 level in Canada and the US. Her fourth foal, the full brother Dreamflight, won the Gr.3 Prix Thomas Bryon and the Listed Prix Omnium II. Another full brother, Herman Hesse, was Group-placed in Australia, third in the Gr.3 Colin Stephen Handicap, and the half-brother Questionare (Galileo), a winner, was stakes-placed in Ireland.

Second dam Truly A Dream (Darshaan) won the E. P. Taylor Stakes when it was a Grade 2 and has six other winners. They are headed by the sire Catcher In The Rye (Danehill), second in the Gr.1 Poule d'Essai des Poulains, and include Truly Yours (Barathea), a two-year-old winner in France and the dam of the Listed winners True To Form and Truly Mine. Truly A Dream is the third dam of Only Mine (Pour Moi), winner of the Gr.3 Lacken Stakes.

Third dam Truly Special (Caerleon) won two Group 3 races. She is the dam of the sire Wareed (Sadler's Wells), winner of the Gr.2 Prix Chaudenay and third in the Gr.1 Gold Cup, and of Solo De Lune (Law Society), who was Listed-placed in Germany. Solo De Lune bred the Group 1-winning half-sisters Cerulean Sky (Darshaan), winner of the Prix Saint-Alary, then a Group 1, and Moonstone (Dalakhani), winner of the Gr.1 Irish Oaks and second in the Gr.1 Oaks, as well as L'Ancresse, a Listed winner and second in the Gr.1 Irish Oaks, Diner De Lune, a Listed winner in France, and Demurely, second in the Gr.3 Give Thanks Stakes. Her grandchildren include Sibila Spain, winner of the Gr.2 Prix du Muguet, Master Of Reality, winner of the Gr.3 Vintage Crop Stakes and Group 1-placed, and two winners of the Gr.3 Chester Vase: US Army Ranger (Galileo), also second in the Gr.1 Derby, and Memphis Tennessee, later third in the Gr.1 Irish Derby.

Cerulean Sky is the dam of Honolulu (Montjeu). Also from the family are Naval Crown (Dubawi), winner of the Gr.1 Platinum Jubilee Stakes and now a sire, and Colette (Hallowed Crown), winner of the Gr.1 Empire Rose Stakes and the Gr.1 Australian Oaks.

Dream Peace has a 2021 colt and a 2023 filly by Sea The Stars, and a yearling filly by Le Havre.