Is this a normal thing?

[Pedigree Ann]

I'm doing this from memory, so if I get the details wrong, kindly forgive me.

Del Carroll, who must have been David's father or grandfather, had taken out a particular handful of a horse named Sportin' Life for exercise at Keeneland. Some time later, horse was found running loose and Carroll found fatally injured on the track. Details never discovered, no witnesses. [Oddly enough, no conspiracy theories floated about. It was a simpler time.] So it is something of a Carroll tradition to ride the horses they train.

Sportin' Life went on to sire Bet Twice, who tried to trip up Alysheba in the Derby stretch, then went on to win the Belmont.