Katey Sagal playing Kaley Cuoco's mum again on The Big Bang Theory

Katey Sagal is reuniting with her former TV daughter Kaley Cuoco to portray her mother on The Big Bang Theory.

The Sons of Anarchy star was announced as a new addition to the cast of the hit comedy series on Friday (22Jul16), during the show's annual panel at San Diego, California's Comic-Con event.

Cuoco has portrayed Penny on The Big Bang Theory since its launch in 2007, and in the upcoming season 10, fans will be introduced to her mother Susan, and brother Randall, played by another new castmember, Jack McBrayer. The 30 Rock actor made a surprise appearance at Comic-Con to celebrate the news.

Katey is no stranger to playing Kaley's mum onscreen after co-starring in family sitcom 8 Simple Rules from 2002 to 2005.

Showrunner Steve Molaro told the crowd at the panel, "Katey has played Kaley's mum before on 8 Simple Rules, and she told us she's always up for playing Kaley's mum."

Sagal and McBrayer joins a cast which also includes Johnny Galecki, Jim Parsons, Kunal Nayyar, and Simon Helberg.

Meanwhile, Molaro also revealed the show's writers have started to contemplate how they would wrap up each characters' storylines, but they have yet to decide when to conclude the series for good.

"I'm not gonna tell you," he replied to fan, who inquired about a possible end date. "There's been a few thoughts that have floated around, but we don't really know how long the show's going to go on for, so I think it's a little early for us to be thinking about an end point."

The Big Bang Theory returns to screens in September (16).