It's a family affair when the Cassidys -- Shaun, David, Patrick, Ryan and Patrick's wife Melissa -- return to TV for a new comedy loosely based on their life.

David and Patrick star, Shaun is executive producer, Melissa is the choreographer and Ryan is the set decorator on ABC Family's "Ruby & the Rockits," premiering tonight at 8:30 p.m.

"It is the best chemistry I have ever experienced, including 'The Partridge Family,'" David tells ET. "My brothers and I are really close. We have always had separate managers or agents. We have never tried to use each other. We never had brotherly competition. It has always been supportive and they are my best friends."

"Ruby & the Rockits" is loosely based on the Cassidy brothers' lives. Patrick plays Patrick Gallagher, a former '80s pop star who has chosen to lead a quiet life with his wife, Audie (Katie Amanda Keane), and two sons -- Jordan (Austin Butler) and Ben (Kurt Doss). But when his former Rockits band mate and brother, David (David Cassidy), shows up unexpectedly with his new-found teenage daughter in tow, Ruby (Alexa Vega), the Gallagher's family life becomes anything but normal.

"Some of the stories and some of the context of the show [are similar to my life]," David says. "Ruby showing up … In my case Katie [David's real-life daughter who recently starred on "Harper's Island"] and I did not get to know each other until she was 12, and now we are very close. She never lived with me."

For Patrick, aside from working with his family, one of the best parts of the series was the fact that he didn't have to audition for the part.

"I got to sit on the other side of the table and watch other actors come in and audition and, boy, that is a learning process that every actor should experience," he tells ET.