Former 'My Three Sons' star Don Grady died yesterday. He was 68. He reportedly had cancer, but there's no official word on a cause of death.

Don played Robbie Douglas, one of the three sons. He was on 'My Three Sons' for most of its run, from 1960 to 1971. It went on for one season after that.

His former co-star Barry Livingston broke the news on Facebook. He said, "My dear friend and TV brother Don Grady passed away today. He was an inspiration to me in so many ways." (Barry played Ernie, the adopted son.)

Don was an original Mouseketeer on the 'Mickey Mouse Club', and was also a musician. He put out a few albums, helped compose the music for 'Switch', the 1991 comedy starring Ellen Barkin and Jimmy Smits and he composed the theme music for 'The Phil Donahue Show'!

If you don't already have it committed to memory, you can find the 'Donahue' theme song on YouTube.  And here's the theme to 'My Three Sons'.

William Frawley, a.k.a. Fred Mertz from "I Love Lucy", was also on "My Three Sons".  He played their live-in grandfather for the first five seasons, but he died during the sixth season of the show.

Here's a video of the first episode where you can see both William Frawley and Don Grady.  Skip to the 5:35 mark.  Hard to believe it lasted 12 years.