The sport of horse racing might have started with the simple question of whose horse is fastest, but centuries of such challenges have morphed that humble query into a full-fledged industry, replete with stories of great horses and the humans behind them. Racing reflects the world it inhabits, a mirror for the societal and economic conflicts playing out in the background.

In horse racing, the practice of matching a stallion with a broodmare to create a potentially world-class Thoroughbred is a world unto its own. Many people spend a lot of money, time, and mental focus on finding just the right male-female combination that can hit the genetic lottery and result in a Triple Crown or Breeders’ Cup winner. When it does happen, the pairings become part of horse racing history – so to celebrate Valentine’s Day, here are five notable Thoroughbred “couples” from the past 20 years or so whose offspring have made mom and dad proud.