They've reimagined the supporting roles
Charlie Gillespie will play Maggie’s high-school boyfriend, Brian, and Ellen Tamaki will play Nico, a detective whose "romantic relationship with one of the sisters" -- probably Mel -- "complicates her investigation." As TV Guide points out, the two appear to be new takes on the original series’ Andy Trudeau (played by Ted King). Andy was a detective whose high school relationship with Prue (Shannen Doherty) complicated his own investigation.
Man in the High Castle’s Rupert Evans has also joined the cast as Harry, a professor with "an infuriating charm and a mysterious interest in the three sisters," according to TV Line. That description means he’s the show’s new Leo, played by Brian Krause in the original, who was the Halliwell sister’s Whitelighter, a guardian angel figure who protects and guides witches. (Sort of like Giles on Buffy.) In the old series, Leo fell in love with Piper (Holly Marie Combs), the middle sister, and the two had three children.
Ser’Darius Blain is also onboard to play Galvin, described by Deadline as "the ideal boyfriend -- funny, mellow, in touch with his emotions, totally on board to follow his lady across the country for her dream job." It was confirmed at TCA that Galvin is, in fact, Macy’s boyfriend. But that doesn’t mean things won’t change down the road; as fans will recall, Leo and Piper didn’t get together until much later, so it’s possible we’ll eventually get a love triangle.
Like Macy, Galvin is a scientist, which was changed for the pilot from his original profession as a filmmaker. "I loved that they changed my character...," Blain said at TCA. "Because I was a science nerd when I was a kid and now we have a black scientist on TV."