American Theorem is out of the unraced Mighty Renee (Maria's Mon), who has six winners and five black-type performers from seven foals. They include the graded stakes winner Mighty Caroline (Stormy Atlantic), successful at Grade 3 level, the multiple stakes winner Cyclogenisis (Stormy Atlantic), the juvenile Listed winner Renee's Queen (After Market) and Viel Spass (Kitten's Joy), stakes-placed in Japan.

Second dam Margy (Theatrical) was also unraced. She is a half-sister to For All We Know (Stephen Got Even), a Grade 2 winner, and to two sons of Strawberry Road, the dual Listed winner Hustler and Robb, who was placed at Grade 2 level and became a sire.

Third dam Over All (Mr. Prospector) was a multiple Grade 1 winner.

Over All's wider family also includes Conquistador Cielo, Horse of the Year in 1982.

Mighty Renee has a two-year-old colt by Classic Empire.