Patricia and (inset) Richmond Arquette Patricia and (inset) Richmond Arquette

It's been a while since Medium (Mondays at 10 pm/ET on NBC) star Patricia Arquette worked with her older brother, Richmond he directed her in her first film, "a whodunit called James Long, when I was only 7 years old," recalls the actress. But she'll finally get the chance to team up with him again when he guest-stars later this season on her hit series.

In the episode, Richmond (Scream 3) will play a man whom Patricia's Allison DuBois meets after he goes to the hospital for an MRI. "While he's in the machine, Allison sees thoughts in his head," explains executive producer Glenn Gordon Caron. "And one of them is an apparently incongruous, violent vision from the past, and she becomes intrigued."

Richmond actually came close to appearing in the series last season. He auditioned to play Allison's younger brother but didn't get the part because "he was a minute or two too old for the role," says Caron of the 42-year-old actor. However, the producers liked him enough to develop this part for him. And while it will be his first time in front of the Medium cameras, it won't be the first time he's helped out with the series.

"He coached me for the pilot and really helped me plot out my character," Patricia says. "He gave me a lot of the insight into Allison that I still use on the show."

Naturally, she's excited to work with the sibling who gave her that big break way back in elementary school. Still, she's also campaigning to convince the rest of the acting Arquettes including sister Rosanna, brother David and sister-in-law Courteney Cox to make time for Medium as well. "I'm hoping they'll do me the favor at one point or another," she says. "The best actors I know are in my family."