The girls were
Marcia,
Jan, and
Cindy; the boys were
Greg,
Peter, and
Bobby.
The actors playing them were
The mother was
Florence Henderson, the father was
Robert Reed, the
housekeeper Alice was
Ann B. Davis, and the scripts were by
Harold Pinter, okay I made that last one up.
The first episode, "The Honeymoon", was shown on 26 September 1969, and the last show went out on 8 March 1974, a total of 117 episodes. There was a variety special made in 1977, featuring H.R. Pufnstuf and many other famous singers and suchlike. This led to more of the ghastly things, then various new follow-up series where they get married, get old, die, get buried, and so on, none of which had any of the charm (Footnote 1) of the original series.
Footnote 1. You watched it and enjoyed it when you were young same as I did. I'm not saying I'd watch it now. If you want the full monty see www.bradyworld.com.
Okay, I did have this fairly serious thing for Maureen McCormick. Who didn't? Second favourite, only: no-one could displace Susan Dey in the Partridge Family, the thought of whom still makes me melt and bubble.