I was watching a special on TV one evening a few years ago. It was on a channel like Family or Hallmark. Might have been the Odyssey or Faith Channel. Anyways...

It was filmed in the 70s. Probably a few years after My 3 Sons ended. "Ernie" and "Chip" were the two sons of a family who were visiting their grandmother in the nursing home on Christmas. It was kind of depressing because she didn't seem to know who they were. They were all going back to their car but "Ernie" stayed behind and held his grandmother's hand. He had tears in his eyes. Suddenly she starts remembering their times together before her memory started fading.

The whole show lasted about 1 hour. It looked like it may have originally been an Afterschool Special or something like that.