John Grayson

John Grayson was the father of Dick Grayson and the wife of Mary Grayson. The three of them performed at Haly Circus as trapeze artists called the Flying Graysons. John and his wife were both killed by a mobster named Tony Zucco, who sabotaged their circus act and caused them to fall to their deaths. It was then that Bruce Wayne took John's young son Dick Grayson in to live with him as his ward, and trained him to be a superhero called Robin.

Reference
Super Friends (Season 1)
 * The Planet-Splitter