By Alex Witchel

At Cafe Luxembourg, the waiter approached just as one of . the two women was leaving for the ladies’ room. “I know what she wants - we always get the exact same thing,” the other said. Ordering the chicken paillard, she asked, “Can we share one?” Well, yes, the waiter said, though each could have her own. That idea hadn’t seemed to occur to either of them.

For years now, Louise Oxhorn and Lynne Oxhorn-Ringwood have been sharing their lives; Louise married Lynne’s ex~ husband, Greg, in 1990, and she is the stepmother of Lynne’s son, Evan. Greg and Lynne had divorced in 1987, and later that year he met Louise. The women became bitter enemies, a situation further aggravated by the custody arrangement for Evan, which called for him to spend alternating weeks in each parent’s house. Their enmity continued until the day in 1998 when Lynne saw Louise wearing a pair of strappy sandals almost identical to her own. One nuclear explosion later, the two decided to change their ways and have now written a book, “Stepwives: 10 Steps to Help Ex-Wives and Stepmothers End the Struggle and Put the Kids First” (Fireside), along with Dr. Marjorie Vego Krausz, a marriage and family therapist.

“We never really knew what to call each other,” Ms. Oxhorn-Ringwood said. “When Evan was a kid, I would call Louise my ex-husband’s new wife, but after 10 years I couldn’t I do that anymore. We came up with stepwives to describe the relationship between ex-wives and current wives.”

Ms. Oxhorn nodded. “Usually stepwives hate each other,” she said, “but when they learn to get along they become what we call co-mamas.” In addition to writing the book, the two women and Dr. Krausz have started the CoMamas Association (www.comamas.com).based in San Diego where they live. It sponsors seminars and support groups and has devised its own workbook to help stepwives learn how to put their differences aside and be more effective parents. Its Web site has registered responses from more than 10,000 women since it was founded in 1999, many of whom answered questionnaires that provided material for “Stepwives.” The association uses as its slogan” Step into her shoes.”

Certainly, with today being Mother’s Day, that’s advice to heed. For one, two or maybe three families in the country, the holiday will have the rosy glow of a cotton commercial: the breakfast in bed will not spill onto the heirloom quilt, the flowers will arrive without looking as if they spent the better part of the day in the delivery truck and the man of the house will cook a five-course meal for his in-laws with a big fat smile on his face. Everyone else, however, has a few adjustments to make.

“We did so many things wrong, but we always did Mother’s Day right,” Ms. Oxhon-Ringwood said of their arrangement to split the day. “Louise did countless things for Evan all the time, and she deserved my respect. I could never verbalize thank you, but that was my way of acknowledging what she had brought to Evan and to my life.”

Ms. Oxhon noted that Mother’s Day can be a touchy day for stepmothers, who live in a society where the word has not quite shed its Brothers Grimm connotation. “As painful, as that is, think how painful it is for a mother to have to share her kids on Mother’s Day,” she said. “You have to empathize with your stepwife. And by sharing the day we allow Evan to feel good about himself and not disloyal, that if he likes his stepmother it will make his mother feel bad.”

That empathy and respect, along with the effort to focus on what is best for the children, form the basic tenets of the transformation from stepwife to co-mama. “It’s not that the women are bad,” Ms. Oxhon said. “But the situation they find themselves in brings out the worst in them. They’re predisposed to dislike each other.”

Indeed, the dichotomy that usually defines the stepwife relationship as it begins is that the most joyous moment of the new wife’s life coincides with what can be the most devastating for her predecessor.

“It was one of the saddest days of my life,” Ms. Oxhon-Ringwood recalled of the day her husband of 15 years remarried. “I felt I had been replaced. I did expect Greg to remarry, but only when I was ready. I realized how many unrealistic expectations I had.”

The women exchanged brief, understanding glances. It seems incredible that they have gotten to this moment, when they can finally be rid of each other - Evan is 19 and just finishing his freshman year in college - and are instead collaborators and traveling companions.

“We see the irony,” Ms. Oxhon -Ringwood said. “But we feel we have a message to carry and are fortunate to be able to do it.” Her co-author chimed in, “We feel a lot better being co-mamas, though we don’t recommend stepwives become friends, which is often unrealistic.” Then her co-author chimed in, “You can get too close and say too much, and the whole thing can backfire. The point is to parent the children and only that.”

In happy accord, they began to eat. Though there are some similarities between the two they are both quite slim and were dressed in black pantsuits - Ms. Oxl;1om-Ringwood, 51, is blond with big green eyes, and Ms. Oxhon, 44, is brunette with big blue eyes. Ms. Oxhon-Ringwood seems the calmer of the two, but she is also the one who usually speaks first: first wife, first voice. She has also remarried, and understands the stepwife conundrum from both sides now.

Ms. Oxhon, however, attacks her food with an almost manic energy, slicing the chicken into Cuisinart-like ribbons. She has been unable to have children and seems grateful for the relationship she has built with Evan, though she does not discuss it in interviews. In accordance with the “limits and boundaries” recommended in the “Stepwives” program, she and Ms. Oxhon-Ringwood have agreed that questions about Greg are answered by his wife and questions about Evan are answered by his mother.

“We found that the primal feelings that are triggered in stepwives’ relationships are territory issues,” Ms. Oxhon-Ringwood said. “That’s what causes the conflict and the fighting.”

The numbers of families doing that fighting seem to be on the rise. Dr. Margorie Engel, president and chief executive of the Stepfamily Association of America (www.SAAfamilies.org), a nonprofit organization dedicated to successful stepfamily living, says that statistics on stepfamilies err on the low side. In an interview, she said that while the 2000 census put the number of children living in stepfamilies at 16 million, that is based “only on those children whose mother is the custodial parent.”

“It doesn’t include people living together or unwed mothers or gay and lesbian couples,” she said. “So you can see how wrong that number is.”

While family combinations ;can seem endless these days, the most common still involve what the “Stepwives” authors call “the man in the middle,” who, in their book at least, seemed somewhat absent during their lo-year battle. Wasn’t his the cooler head that should have prevailed?

Ms. Oxhon leapt to his defense. “Greg did take responsibility,” he insisted. “It’s just that I didn’t like it that he talked to Lynne, so there were times I did take over.” Well, wasn’t that rather childish? They are the parents, after all. Ms. Oxhon nodded sheepishly and took a big gulp. “I can say that I was extremely immature,” she said. “When Lynne and I were struggling, he .tried very hard to get us to get along. He really tried.”

Mr. Oxhon, in a telephone interview, said: “If I felt the tension level getting too much, I told them I would step in and take control, and I did. I only wanted us to stay focused. on having a healthy kid. Sometimes, when they would lose sight of that, it was like watching two children play, getting more aggressive, and I w01l1d say, ‘Enough - go to your comers.’ To their credit, they were always willing to look at it. Louise wan1ed very much to be a part of Evan’s life, but it had to be not at the expense of his mother.”

As if to comfort her stepwife, Ms. Oxhorn-Ringwood also admitted. to her own bad behavior, like refusing to sit with her ex-husband and Louise at school functions. “For me, as ‘the mother, I felt like every happy event in my son’s life was clouded by Louise being there,” she said. “I thought of her as my karmic punishment for leaving my marriage.”

Ms. Oxhorn looked startled. “Isn’t that a nice compliment,” she said somewhat tremulously. Ms. Oxharn, Ringwood shot her a steadying glance. “That’s the beauty of being able to come out of adversarial positions to the other side,” she said. Her ‘” co-author nodded, mollified, as Ms. Oxhorn-Ringwood went on to say that since the two started working out their differences, Evan has been happier.

“I think that part of the ex-wife’s responsibility is to acknowledge that it’s not easy to take care of someone else’s child,” she said. “And even though you would rather be doing it yourself, it doesn’t negate the fact that she’s doing it.”

Well, it seems their next step is to become co-grandmamas. They nodded eagerly. “The point of our program is that it never ends,” Ms. Oxhorn-Ringwood said. “It’s not over when a child turns 18.”

Ms. Oxhorn added: “We speak. to families where the children tell their parents, We don’t want any of you coming to the hospital because ~u still can’t get along.’ So who wins in that situation?”

Ms. Oxhorn-Ringwood smiled placidly. “You have to keep the skills you developed, the respect and empathy,” she said. “The stepmother is entitled to come to the hospital, too. There’s room for everyone.”