David Cassidy, who played Keith, was hung like a horse.
Susan Dey, who played Laurie, was in love with David Cassidy, and they fucked once, but David was not impressed with Susan in bed, and thought she was too goody-goody. Susan suffered from a severe eating disorder.
Jeremy Gelbwaks, who played the first Christopher, was an obnoxious brat on the set and could not get along with the other actors; therefore, he was recast.
Danny Bonaduce, who played Danny, had a very troubled upbringing, and David Madden, who played Reuben Kincaid, allowed Danny to live with them.
Shirley Jones whose character was Shirley, was very sexual, and she and Jack Cassidy, her husband at the time, would fuck all over the set.
Need I say David Cassidy, Keith Partridge, was a very troubled soul. I know David's first wife did not want to have sex with him. He said, not verbatim, I have hundreds of thousands of women who want me and I married the one that did not want me. Jack Cassidy was very jealous of David’s success.
Suzanne Crough, who played Tracy Partridge was the first to die.
Okay, that’s all I know. Please correct me for any misrepresentations.