Speaking of show business dynasties, character actor Jack Cassidy (who starred with Paul Anka in Look in Any Window) married musical theater star Shirley Jones in 1956 (they divorced in 1974). They had three children of their own. After their divorce in 1974, Shirley Jones married comedian Marty Ingels, who helped her raise the youngest two.
David was born to Jack Cassidy and his first wife Evelyn Ward in 1950. By 1970 he was starring with stepmom Shirley Jones in The Partridge Family (1970-74) and establishing himself as the top teen idol of his generation. But he also did some tv and movie work, including his own series, David Cassidy: Man Undercover (1978-79).
2. Shaun, born in 1958, became a tv star of his own in the gay-subtext Hardy Boys Mysteries (1977-79). He also had a teen idol career before becoming a writer, director, and producer.
He's appeared in lots of other tv series and tv movies, including two versions of the Superman myth: he played the villainous Leslie Luckinbill in three episodes of Lois and Clark (1996) and Henry Small, the father of Superboy's girlfriend Lana Lang, on Smallville (2002-2003).
Joseph and the Amazing Technicolor Dreamcoat. He's also been in The Music Man, Annie Get Your Gun, Camelot, and 42nd Street.