Good Guess is the fifth foal and fourth winner out of the unraced Zykina (Pivotal) and is the latest known foal of his dam. He is a half-brother to Spangled (Starspangledbanner), winner of the Gr.3 Sceptre Stakes, and to the Listed-placed sprinter Jumira Bridge (Invincible Spirit), who won nine races.

Second dam Russian Rhythm (Kingmambo), champion 3-year-old filly in Europe in 2003, won the Gr.1 1000 Guineas, the Gr.1 Coronation Stakes, the Gr.1 Nassau Stakes and the Gr.1 Lockinge Stakes, and bred four winners. Her Listed-placed daughter Safina (Pivotal), a full-sister to Zykina, produced Potapova (Invincible Spirit), winner of the Gr.3 Atalanta Stakes, and Marenko (Exceed And Excel), winner of the Gr.3 Fred Darling Stakes. Russian Rhythm is also the grandam of Bashkirova (Pivotal), winner of the Gr.3 Princess Elizabeth Stakes, and of the Group 3 winner Zonderland (Dutch Art), and great-grandam of the Group 3 winner Positive (Dutch Art).

Third dam Balistroika (Nijinsky) was unraced and produced nine winners besides Russian Rhythm, among them the Group 2 winner Perfectperformance (Rahy). She is a half-sister to Park Appeal (Ahonoora), a dual Group 1 winner who took the Gr.1 Moyglare Stud Stakes and became an outstanding broodmare as the dam of the champion sire Cape Cross.

The wider family includes Alydaress (Alydar), winner of the Gr.1 Irish Oaks, and the champion Shadayid (Shadeed), winner of the Gr.1 1000 Guineas.