Nepotism is not unknown in the TV business, but with his latest project, Shaun Cassidy has taken family ties to a new extreme.

Cassidy is the 1970s teen idol who has spent the past 15 years as a television writer-producer of cult dramas with a sci-fi bent ("American Gothic," "Invasion"). Now he has turned his attention to musical comedy with ABC Family's "Ruby & the Rockits," about two middle-aged brothers, former rock gods who become reacquainted after the long-lost daughter of one of them re-enters the picture. The series premieres its 10-episode run Tuesday night.

For the cast, Cassidy stayed close to home -- literally. One of the leads is his half-brother, David, who had his own heartthrob stint as the lead singer on "The Partridge Family," the early '70s sitcom about a family of rock singers that "Ruby" deliberately echoes. The other is stage actor Patrick Cassidy, the younger brother whom Shaun freely admits torturing endlessly during childhood (and well beyond, according to Patrick). The clannishness doesn't stop there: Ryan, the youngest Cassidy brother, works behind the scenes as the show's lead set dresser. (The title character, David's 15-year-old daughter, is played by former "Spy Kids" star Alex Vega.)

Is it all too twistedly self-referential? As the writer in the family, Shaun Cassidy is aware of the dangers.

"The double-edged sword of working with family is it can be the most fulfilling experience you've ever had," Cassidy, 50, said during a recent interview in his office on the CBS lot, where "Ruby" is filmed. "But the flip side is it can also be the most tortuous and most stressful, because it's your family and the lines can get blurry."

The brothers are all sons of Jack Cassidy, the comic actor whose presence continues to hang over the family nearly 33 years after his death. David is the son of Cassidy and Evelyn Ward; Cassidy later married actress Shirley Jones, the mother of Shaun, Patrick and Ryan. Jones, in a paradoxical twist, played David's birth mother on "The Partridge Family."

According to Shaun, his father's personality, on-screen and off, inspired the character of David Gallagher, the narcissistic performer whom David Cassidy plays on "Ruby." ("It's just who he is. It's very larger than life," Patrick, 47, says of David's character on the show. "Everything is extreme.")

Even today, the sons seem to wrestle with ambivalent feelings toward their father. David has described Jack in interviews as an alcoholic, a sufferer of bipolar disorder and a closet bisexual who broke his heart by abandoning him when he was young.

But for this story, David, who at 59 has thinner hair but is nearly as lean as during his pop-idol days, offered a balancing perspective: "If you put all my brothers together, we would add up to all the talent that was in my father."

Cassidy found more fame on ABC's "The Hardy Boys/Nancy Drew Mysteries," then spent much of the 1980s in the theater. But by the time he co-starred with David in the Broadway hit "Blood Brothers" during the early 1990s, Shaun had tired of performing. His writing and producing career got an early boost in 1995, when CBS picked up "American Gothic," the satirical sci-fi series he made with director Sam Raimi. The show retains a cult fan base even though it ran for just one season. During the 2005-06 season, ABC aired his alien-takeover series "Invasion."

With "Ruby," Shaun saw a way for the family to work together in a project that would recall another Cassidy opus. "He said, 'I kind of wanna do a new "Patridge Family," ' " said Kate Juergens, head of programming for ABC Family.

The premise has David and Patrick Gallagher, hit-making brothers behind the '80s group the Rockits, who find their lives upturned after David's daughter Ruby re-enters the picture. Patrick settled down and became a car dealer and family man; David is still playing small casinos and chasing a comeback. Asked if he'll find a part for his mother, the 75-year-old former "Partridge Family" matriarch, Shaun replies: "We haven't written her in yet, but it's coming. She comes to every taping."