Gotta be Frank Furillo & Joyce Davenport. With the Huxtables a close second.
Nah. The parents on 7th Heaven. They had, what, seven kids? Or maybe the Waltons, same reason.
Xander and Anya on BtVS. Well, mostly Anya and Xander just does his best to keep up.
Morticia and Gomez Addams.
Mais oui!
Biffy! That’s French!
I don’t watch the show much but I know that every episode of Dharma and Greg that I’ve ever seen by accident involves them humping, or talking about how much they enjoy it, or talking about how great/disgusting it is that their parents do it.
The two “teenage” couples in “That 70s Show.”
Paul and Jaime Buchman must be somewhere on the list.
What about Elizabeth and Coach Lubbock? I mean, Jesus, “Just the Ten of Us”??
Mike and Gloria Stivic.
Jonathan and Jennifer Hart in Hart To Hart.
Sydney Bristow and Michael Vaughn on Alias. Not that I’m complaining.
Mmm…Jennifer Garner.
Rob and Laura Petrie.
The parents on “Malcom in the Middle”.
That’s who came to mind first thing when i read the title of the thread. 
Well, I agree with the OP. When I read the title of this thread I thought “It’s gotta be Captain Furillo and Joyce!”
I second the parents in “Malcom in the Middle”- I know in one episode, Hal is feeling jealous that his friends are always better at him in everything, but the subject of how often they have sex comes up, and Hal has way more than any of his friends- but I can’t remember the exact number.
Well, considering the episode where they become exhibitionists, I could argue for Marge and Homer Simpson.
Monica and Chandler. Doin’ it, doin’ it, phone doin’ it.