I can't stand stage brats," says Carollyn McNichol. "I want my kids to be down-to-earth and normal. When they start taking themselves too seriously, I remind them that one day they will not be as hot as they are now."

Thankfully, Carollyn's daughter Kristy is too savvy to react to her mom's preachment with a disgusted "Yucka!" That's the undeleted expletive Kristy has made famous as the tomboyish Buddy on ABC's quality living room series Family. Though she's all of 15 and barely out of her Donny Osmond purple knee socks (the badge of every Osmond fan), Kristy's getting to be as big a star as her old Osmond idol. Already into her third season as the wise-beyond-her-years runt of Family, Kristy came into her spunky own last month when she copped a surprise Emmy.

Over on CBS meanwhile, Kristy's lookalike big brother Jimmy, 16, is breaking in his own series, The Fitzpatricks, a blue-collar version of The Waltons. Though he's an old pro of 80-odd TV commercials (Crest, Opel, Kool-Aid), Jimmy competitively figures his show came along just in time to keep even with his upstart kid sister. "Thank God," Jimmy sighed on hearing that CBS bought The Fitzpatricks, "I can now hold up my head in this family."

Mom frowns on sibling rivalries that "get kind of loud at times," but she is relaxed enough "to stay pretty loose about it." In contrast to the Family and Fitzpatricks clans, both headed by dutiful fathers, Carollyn, 34, is a hardworking mother who's raised her kids single-handed. At 22, she was divorced from their carpenter father and left with three babies. (The youngest, Tommy, now 12, was raised by Carollyn's parents and lives with them in Burbank.) Carollyn worked as a secretary, cosmetics saleswoman and sometime movie extra. (She is also youthful enough to be a stand-in for both of her kids on their shows.)

Kristy started acting at 8 because "my mother was in the business and my brother did commercials. I wanted to try, too. So Mom took me for some commercials, which I got. I can't imagine any better life." After pitching for Kentucky Fried Chicken and McDonald's, Kristy moved over to guest shots in Bionic Woman and Starsky and Hutch and a regular role in CBS's ephemeral 1974 series Apple's Way.

At the time Jimmy "felt sort of left behind." One TV pilot was a flop and his own high jinks got him busted from the original cast of Little House on the Prairie. "Jimmy gets himself into trouble with as little effort as anyone I've ever seen," Carollyn groans. "First he got into trouble with the teacher on the set because he couldn't sit still. Then he tossed a borrowed pencil back to a girl in the cast and nicked her eye. He was written out of the show."

These days the McNichols are what Jimmy calls "just an average family" in their home-of-the-moment in Tarzana, Calif. (The family rotates between three condominiums and owns seven houses in which Carollyn has invested the kids' earnings.) Instead of heading for school, Jimmy is driven to Burbank and Warner Bros., while Kristy heads over the Santa Monica Mountains to 20th Century-Fox. Both kids are tutored on the sets between takes. As Carollyn justifies it, "Schoolchildren nowadays are forced to make choices about drugs and sex that could change their lives forever. My kids are escaping that pressure."

Kristy doesn't have a steady boyfriend. "I'm too young for that kind of thing," she says. Instead, "Kristy and I have the same group of friends and go to the movies and hang out together," Jimmy says. Kristy chirps, "I'd love to meet Jodi Foster and Tatum O'Neal. I hear they're great." On her sets Kristy buzzes around in an electric golf cart and does wheelies on her XR-75 Honda dirt bike. "Kristy is a wonderful, strong young personality," says her Family mother, Sada Thompson. "She's both spontaneous and thoughtful."

Jimmy is allowed to date but scoffs, "I don't have just one girlfriend. I like a choice." Actually, most of his 5'8", 130-pound libido goes into sports. He's an accomplished diver—"I can do a four-and-a-half backward layout"—and tennis player. "I really wasn't worried about not making it as an actor," he boasts. "I figured I could have made it as a tennis pro."

The indication of Kristy's recent maturing—beyond the two inches she sprouted in the last six months (up to 5'2")—is that Donny Osmond has been replaced in her heart by—Yucka!—Burt Reynolds. She plays Burt's daughter in The End, co-starring with Sally Field, Robby Benson and Joanne Woodward. "He says he wants to adopt me," she blurts, "and I'm ready."

That might not fit Carollyn's plans to keep her kids' egos deflated. "She's been the little princess since she met Burt," Carollyn says. "But nobody around here pays much attention to her. Acting is fine, but the first time they get turned down for something and are heartbroken about it, it's all over. When it's fun, that's one thing. But if it's not, I'm going to put a stop to the whole thing."