SHOWS FOR YOUNGSTERS AND THEIR PARENTS TOO : ‘Sister, Sister’ can you spare us a clue? Which one are we really talking to?

It just sounds like stereo.

To get any individual sense of either Tia or Tamera Mowry, stars of the WB sitcom “Sister, Sister,” you must get them to talk on the phone one at a time. Because when they’re both on the line, they’ll talk in unison--and give the same response.

Despite their many acknowledged similarities, the 17-year-old identical twins are the first to point out their differences: Tia’s voice is higher. She’s neater, too, and it’s Tamera who has the mole under her left cheek. (Tia’s mole on the show is just that, for show.)

“Yeah, they put that mole on me, but they dress us differently, since our characters are supposed to be that way,” Tia points out from the Manhattan hotel room where the twins are on a whirlwind publicity tour.

On “Sister, Sister” they play Tia Landry (Tia) and Tamera Campbell (Tamera), twins separated by birth, raised, respectively, by a single mother and single dad, played by Jackee Harry and Tim Reid. They now all share a home.

“Sister, Sister” presents twins whom, the Mowrys say, are quite different from each other and from the girls in real life. Tia says the Mowrys had no input into the Paramount show developed for them.

“We’re much more alike than what we play,” Tamera points out. Off the set, the girls always dress identically. “We have the exact same taste. If we see something we want and there aren’t two sets of it, then we don’t get it.” They like clothes chosen for Tia’s character better than Tamera’s. Says Tia: “We wouldn’t wear the funky colors and cut-up stuff they put on Tamera.”

Don’t they worry about their individuality?

“No,” Tamera says firmly, with Tia chiming in the same sentiment. “I love my sister. She’s my best friend.” Although Tamera confesses to “a week in ninth grade where I tried to make myself look different, by wearing a jacket over our matching outfits. But that didn’t last too long.”

Now, they’re back to the way they like it: just like each other.

Seven years ago, they were “military kids living all over Texas” who decided they wanted to be on stage. Ten beauty pageants later, they had five trophies each. “It was weird,” Tia says, explaining she’s the better dancer but Tamera sings best. “We did win every contest we entered. And even though we were competing against each other, we always said it was all right if one of the Mowrys won.”

The girls then decided to become actresses. “We begged our mom for, like, four months,” Tia says. When their mother finally told them they would go to California, they had a month “to get something .” The girls got two projects: an industrial film and a Chrysler commercial.

Their mother, in the communications field for the military, quit her job. Their father, also in the military, retired, and the entire family--including younger brother Tahj--moved to California, where the girls cut a strong path through television commercials and welcomed another brother, Tavior, now 2.

“We were the Barbie girls,” Tia says. “And we were tired with just being called that,” adds Tamera.

Then Tahj, 8, got a recurring role on ABC’s “Full House” (as Michelle’s best friend). “When we saw him on the set, we knew that’s what we wanted,” Tia says excitedly.

They were thrilled when ABC picked up “Sister, Sister” last year. The series held several time slots and was bumped around until it ended up on its popular TGIF lineup, but didn’t dowell enough for ABC to pick it up for the new fall season. “Sister” eventually made its way to the fledgling Warners Bros. network, where a spokesperson says, “It’ll be the exact same show and characters, but will have a new look.”

“Sister, Sister”--and school, the Mowrys both emphasize--are their priorities. Boys take a back seat for now.

When they’re not shooting the show or doing publicity tours--where they’re tutored--they attend Birmingham High in Van Nuys, where they now live.

Acting is their main focus, but should that fizzle, the Mowry sisters plan to attend “the University of Pennsylvania and study law.” And, no surprise, they say it simultaneously.

“Sister, Sister” airs Wednesdays at 8 p.m. and Sundays at 7:30 p.m. on WB/KTLA. For ages 6 and up.