A.P. Indy
Royal Delta's dam was Delta Princess, who won six stakes races before retiring to broodmare duty at Prince Saud bin Khaled's Kentucky farm, where she produced three graded stakes horses. Delta Princess was by another Belmont Stakes winner, leading sire A.P. Indy. The combination of Empire Maker and an A.P. Indy mare created multiple crosses to La Troienne, one of the most influential broodmares of the twentieth century.