Don Grady, who played the eldest son on the [very old] show “My Three Sons”, has passed at the age of 68. Details below.

Marisa Mendez

“Sons” star Barry Livingston just posted on Facebook, “My dear friend and TV brother Don Grady passed away today. He was an inspiration to me in so many ways.”

Grady had reportedly been suffering from cancer.

Grady was an original Mouseketeer on the “Mickey Mouse Club” … before going on to play the role of Robbie Douglas on “My Three Sons” from 1960 to 1972.

Grady was also a pretty successful musician … he’s credited with writing the music for the Ellen Barkin movie “Switch” … and the theme song for “The Phil Donahue Show.”

tmz