The Partridge Family {a studio band except for Cassidy and Jones} came about from another family that in fact were skilled musicians. It was loosely based on The Cowsills another group of that ear who did their own singing and instruments as they grew up. The Cowsills was started by three brothers and sibblings joined as they got older. They turned down the show because the network had already casted Shirley Jones as the mother and they wanted Barbara Cowsill. As a result they turned down doing the show.
The Rain, The Park & Other Things was one of the great pop songs of that era. I often wonder what the Partridge Family would have been like had they decided to do that show.
Many people do not know that Barry Cowsill died in Katrina. I had his autograph at one point, but long lost. He was my favorite. Recently went on a kick watching what happened with the Cowsills on YouTube and it was a really sad story. Abusive father...had bad effect on all the kids...sigh
The young Cowsill girl played the youngest daughter in the first year of the show.