Complex sentence: She was sired by Bel Esprit, winner of the Doomben 10,000 who also sired Bel Mer, a mare who won the Robert Sangster Stakes in 2009.
Split into simpler sentences: She was sired by Bel Esprit, winner of the Doomben 10,000. Apart from Black Caviar, Bel Esprit sired Bel Mer, a mare who won the Robert Sangster Stakes in 2009.