Ralph Waite
I was watching the various reunion videos on YT, and was surprised to learn that he was a minister in his younger years. It wasn't until after he passed, that I realized he was Father Matt on the soap Days. He was a mentor to Eric.
In addition, during the Waltons run, he was involved with the actress that played Miss Beadle on Little House. She mentioned their relationship in her autobio a few years ago.