You haven't bothered to do even a minimal amount of due diligence to confirm your old family story. You haven't read the article, nor the source you've linked to. Your timeline isn't even right.
Teetor's patent was filed in 1948. Your grandfather's patent was filed in 1950. He didn't invent it 1956 as you've said.
The first production car with Teetor's cruise control was rolled off the line in 1958. So where exactly are you getting this idea of Teetor being held up for 14 years by your grandfather's '1956' patent, which would put Teetor's first cruise control production car at 1970?
Even the source you linked in your own posts corroborates the above.