"[Fans] tell me that I was their surrogate father, the one who brought them up," Waite told Entertainment Weekly last year.
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"I loved Ralph very much. He was a kind and funny man with a great social consciousness and a big heart," Thomas tells PEOPLE. "And he was one of the most uncompromisingly honest men and actors I've ever known – a great example for a young performer. Goodnight, Daddy."
In addition to The Waltons, Waite appeared in Alex Haley's miniseries Roots, and had recurring roles on the soap opera Days of Our Lives and the hit CBS drama NCIS.
Here's what the rest of The Waltons cast has been up to:
Michael Learned (Olivia Walton): Toured with a stage production of Driving Miss Daisy and appeared in the independent film Afterlife.
Richard Thomas (John-Boy): Plays Frank Gaad on the FX drama The Americans.
John Walmsley (Jason): Plays and composes music.
Judy Norton (Mary Ellen): Stars on the Canadian police series Bluff and wrote and stars in the indie film Finding Harmony.
Eric Scott (Ben): Owns Chase Messengers, a Los Angeles-based delivery service.
Mary McDonough (Erin): Authored Lessons From the Mountain: What I Learned from Erin Walton . She has a deal for two more books with the publisher Kensington.
David W. Harper (Jim-Bob): After quitting acting and working a series of odd jobs including working for Scott's messenger company, he's returning to school to study business and history.
Kami Cotler (Elizabeth): Is the founding principal of the Environmental Charter Middle School in Gardena, Calif.
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