THE NEW TV SEASON : The Fall Season: From the Outer Limits to Real Down to Earth Problems : Not everybody lives happily forever after

A wedding is about to take place on the military chapel set between Maj. John D. (Mac) MacGillis of the U.S. Marine Corps and Polly Cooper. He’s a Vietnam vet embarking on his first tour of marital duty, she’s a liberal-minded reporter, widowed with three daughters, ages adorable to adolescent.

But before the vows can be said, a matter of protocol must be settled. All activity has ceased while the proper way to hold swords for the traditional cutlery canopy through which the couple will exit is discussed. Military buff and series star Gerald McRaney finally settles it. “You don’t hold the blade down toward the honored couple,” he says. The rehearsal for the fourth episode of CBS’ new fall series “Major Dad” can continue; the newlyweds will safely exit down the aisle. (The episode airs Monday at 8 p.m.)

What can’t be so easily settled is what will happen to the couple after they leave the chapel. They’ll be setting off on a path that statisticians claim real people take 1,300 times a day in this country: They’ll be forming a stepfamily. By the year 1990 (a mere three months off), the Stepfamilies of America Assn. predicts that step- and single-parent families will outnumber the traditional nuclear form. By the year 2000, stepfamilies are expected to be in the majority.

If Mac is anything like the 35 million American stepparents before him, he’ll be faced with emotions and incidents that can frighten, anger and threaten to tear this union asunder. If things work out, he’ll be rewarded with warm and lasting relationships.

Or, he could end up like previous television stepfolks in such cheerful fantasies as “The Brady Bunch.” If, as the advertising campaign for “Major Dad” claims, they’re just “looking for a few good laughs,” reality may not be allowed to interfere.

Television hasn’t been totally blind to the changes in American society over the past 20 years. It took great delight in exploiting the phenomenon of single-parent households with such ‘80s hits as “Who’s the Boss?,” “Kate & Allie,” “My Two Dads” and “Full House.” But these tended to avoid the messiness of real life. Ex-spouses were conveniently dead or forgotten and children weren’t troubled by the specter of a stepparent. Indeed, Mom or Dad were rarely allowed to bring their dates indoors . . . unless they happened to be living under the same roof, as was the case of the hired help in “Who’s the Boss?” Remarriages usually didn’t work, ratings or storywise: When Allie landed a man after five years of living with Kate, he was transferred to a job in another city--in what must be a common stepchild fantasy.

There were also some ill-fated attempts at portraying stepfamilies during this period. Among them was NBC’s 1983 mid-season series, “The Family Tree,” which starred Ann Archer and Frank Converse in a tense, hourlong family drama of a couple’s efforts to bring together two sets of kids. Possibly too real for its time, it was soon axed. That fall, ABC had “It’s Not Easy.” The half-hour sitcom sought humor in two remarried exes living across the street from each other and sharing custody of a pair of kids. The premise proved as impossible as it might have been in real life and lasted just five episodes.

This season, the networks have introduced a new community of prime-time stepfamilies. Sunday nights, ABC’s “Life Goes On,” about a family coping with a Down’s syndrome child, includes a daughter from the husband’s first marriage. NBC is running two limited series featuring stepfamilies on its Sunday night “Magical World of Disney” hour. In “Parent Trap,” Hayley Mills (who as a teen-ager in the 1961 original “The Parent Trap” played a set of twins scheming to get their divorced parents back together) will marry the widowed father of triplets. Referred to by industry insiders as “The Brady Bunch in Hell,” “A Brand New Life” is an hourlong drama-comedy that Perry Simon, NBC’s senior vice president of series programs, says will “capture the bitter as well as the sweet” of stepfamily life. Barbara Eden plays a divorced waitress and mother of three who marries Don Murray, a widowed attorney and father of three.

Monday nights on CBS will be the stepfamily hour as “Major Dad” is followed at 8:30 by “The People Next Door.” This half-hour sitcom features a widowed cartoonist with two kids, a new wife and an imagination with a life all its own.

Among returning shows, “The Cosby Show” on NBC has Lisa Bonet rejoining the Huxtable fold with a new husband and a 3-year-old stepdaughter. J.R. Ewing’s new bride from last season continues as stepmother to his son on “Dallas,” and among CBS’ mid-season replacements is “His & Hers,” about a husband-and-wife marriage counseling team who have custody of his teen-age son from a previous union and hopes of starting their own family.

So is television ready to tackle the truths of this patched-together family form? Not necessarily.

“TV doesn’t want to do stepfamilies,” says Earl Pomerantz, co-executive producer of “Major Dad.” “It’s too complicated. Mom and Dad is easier.”

Pomerantz, a former producer of “The Cosby Show,” drew on his own experiences as a stepfather for the 1988 mid-season series “Family Man.” It was critically well received, but it was bounced from the schedule for the more traditional family fare of “The Ten of Us,” a “Growing Pains” spinoff.

“It’s hard for TV, especially comedy, to do stepparents and do it funny,” Pomerantz says. “A buffoon dad is easy. What is a stepdad? They’re not the most winning characters. . . . A divorced mother marries another guy, she’s not getting back together with Dad. I don’t know what’s funny about that.”

“Major Dad” did not begin life as a stepfamily show. When CBS committed to doing a sitcom with “Simon & Simon” star McRaney, he was pitched as a widowed Marine trying to cope with raising a family alone. The network added its spin by making the household totally female, to contrast with his all-male work environment. And rather than making him a widower, co-executive producer Richard C. Okie says, they paired him with a widow, “so there’s a live, adult relationship happening along with the parenting.”

Television, like many stepfamilies, seems to have the most trouble dealing with the ex-spouses. “Major Dad” is no exception. Okie’s instinct and Pomerantz’s personal experiences led them to kill off the stepchildren’s biological father.

“We thought it was cleaner,” Okie says. “If you add a father, where does he live, when does he come in and what’s his relationship with the family? There’s competition with Mac and already we’re into a whole other potentially heavy and less humorous area.”

They have discovered a payload of humor in the power that Polly’s three girls have over Mac, a common situation between stepparent and child.

“They jerk his chain,” Okie says. “(The kids) realize they have the reins here and they enjoy it. I know it happens in stepfamilies. There are cards that stepkids can play.”

And while many stepfamilies would hope for harmony as soon as possible, “Major Dad” will benefit, its creators believe, by keeping Mac and the children at a distance for at least the first year.

“We started out with characters who are at A and Z,” Okie says, “and we don’t want them to rush to the middle of the alphabet too fast.” Mac may melt to the point of adopting his charges, Okie assures, but it probably won’t be until at least next season.

NBC decided to give its “A Brand New Life” stepfamily a full hour in which to explore the laughter and the tears. “An hour was better suited to the more complicated situation a stepfamily poses,” Perry Simon says.

The premise is that of a working-class waitress and divorced mother of three, played by Eden, who marries a successful lawyer and widowed father of three, played by Murray. On the surface, it might sound familiar, producer-writer Chris Carter acknowledges, but “it’s as far as you can get from ‘The Brady Bunch.’ ‘The Brady Bunch’ had a laugh track, it could be silly, sweet, schmaltzy, smarmy. It was a product of its time. This show will be a product of its time.”

Thus, there will be stress aplenty. The kids will have clashing values and territorial battles, while the new wife dukes it out with the old housekeeper.

The new wife’s former husband will live nearby, occasionally invading their lives. When they decide to put her teen-age daughter in private school, the biological dad will show up to protest. Things probably won’t get much crankier, for now. “I would love to explore the more tragic parts of a blended family,” Carter says. “It’s something you have to build an audience for.” Because his immediate goal is to have audiences and the network begging for more episodes, he feels “the time is not right to test some of those darker waters.”

Thomas Seibt, a therapist and instructor specializing in stepfamilies at the California Family Studies Center in North Hollywood, fears television will continue to take the easy way out in confronting step issues. “If people get the impression that ‘these people are able to work it out, then why can’t we? We must be failures,’ there’s a danger they’ll feel pressure to do better rather than look realistically at their own situation.”

“The reality is, it’s a struggle, and you don’t always succeed,” Seibt adds. The statistics are indeed discouraging: 60% of stepfamilies fail, with 49% divorcing within the first four years.

Still, Seibt is encouraged by the potential benefit to stepchildren when they see families like their own on television. “It helps them feel they’re not so out of place,” Seibt says, “(that) being in this family is normal.”

“When I formed my stepfamily 15 years ago, I naively said, ‘You’ll love this; it will be just like ‘The Brady Bunch,’ ” recalls Mala Burt, a licensed clinical social worker and president of the Stepfamilies of America Assn. “Back then, there wasn’t much information for stepfamilies. (My husband and I) just loved each other and we thought that everything was going to be wonderful--to the point of denying any potential trouble.”

Television was doing the same. “Most of the shows left the impression that you could solve issues in 20-30 minutes,” Burt says. “The realities were glossed over. There were no ex-spouses in ‘The Brady Bunch.’ Everyone called the parents Mom and Dad, so the real relationships were never acknowledged. There were no good role models for stepfamilies showing how to deal with previous families. It was unrealistic both for kids and adults.”

When Donald Reiker and his writing partner and real-life spouse, Patricia Jones, wanted to add more “heat” to the concept for “His & Hers,” a half-hour comedy about a husband-and-wife marriage-counseling team, they gave the husband (played by Martin Mull) a previous marriage and custody of one of his two kids. They also gave him a wisecracking ex-wife. Taking the place of the more typical sitcom fixture--the mildly irritating next-door neighbor--she would hang around the couple’s house and compare notes with the new missus.

When CBS tested the show, however, audiences found the character confusing and unrealistic. The writers had hoped to portray--particularly among characters who are mental-health professionals--a healthy divorce situation. “People had a great deal of trouble accepting the fact the new wife could be friendly with the ex-wife,” Jones says. “We were shocked.” They agreed with CBS, however, to write the character out.

“We think it’s an area that should be tapped,” Reiker adds. “If we had the courage to stay with it, audiences might have loved it.”

Earl Pomerantz says he’ll continue to try to slip some of life’s truths into his shows where he can, but not at the expense of entertainment. And while stepfamilies may soon be an audience majority, he doesn’t believe they want to see a mirror of their lives.

“Television still likes ‘ALF,’ ” he says, “things from another planet that are cute and cuddly. They don’t want to see something with built-in dark clouds.”