Complex sentence: He sired four Grade I winners in his first two crops and in 2006 his son Royal Challenger won the Breeders' Stakes, the third leg of the Canadian Triple Crown, and Seek Gold won the Grade I Stephen Foster Handicap.
Split into simpler sentences: He sired four Grade I winners in his first two crops. In 2006, his son Royal Challenger won the Breeders' Stakes, the third leg of the Canadian Triple Crown, and Seek Gold won the Grade I Stephen Foster Handicap.