Who killed Robin's parents?
Approved answer
The Tragic Fate of the Graysons
As the youngest member of the acrobatic troupe called the "Flying Graysons," Grayson witnesses a horrific event when mafia boss Tony Zucco assassinates his parents to extort funds from the circus that hired them. Following this tragedy, Bruce Wayne adopts Grayson as his legal ward and trains him to become his partner, Robin.