The family of Hollywood legend GENE KELLY has suffered a devastating tragedy – the famed dancer’s 15-year-old grandson died a week after collapsing at a high school sports event.

Seamus Camp – son of the “Singin’ in the Rain” star’s youngest daughter, cos­tume designer Bridget Kelly, and her husband Joe Camp – dropped to the ground while running in a cross-country meet on Oct. 22 near his home in Livingston, Mont.

“After receiving CPR on the course from EMTs, Seamus was admitted to the intensive care unit at St. Patrick Hos­pital in Missoula,” a family source told The ENQUIRER.

“He never regained consciousness and passed away at the hospital on Oct. 28.”

For Kelly’s daughter Bridget, her son’s death brought back heart­breaking memories of losing her beloved dad in 1996.

Kelly – a leading figure in Hollywood musicals through the 1940s and ’50s – died on Feb. 2, 1996, at the age of 83 after suffering a series of strokes.

“Seamus was born the same year that his grandfather passed,” said the source.

“He was his mother’s pride and joy. She said that his man­nerisms reminded her exactly of her father – the way he smiled and the way he talked. The family and close friends are having a difficult time dealing with his loss.”

Seamus’ cross-country coach, Kirk Lentz, told The ENQUIRER that the teen’s sudden passing was a total shock. “There was never any indication that Seamus had any health issues during the two years he participated on the team,” Lentz said.

“He was a great kid. This is just tragic.”