DEAR ABBY: I would like your opinion about a family situation: One of my sisters is marrying my other sister's ex-husband.

My younger sister, "Charlotte," and her husband, "Mel," were divorced because she was unfaithful. My other sister, "Kara," split from her husband because they cheated on each other. Charlotte has three boys and Kara has two girls.

Mel and Kara were both hurting, so they began to console each other. Well, one thing led to another. They have been living together for some time. This has devastated Charlotte. She and Kara used to be close. They no longer speak.

Kara has announced that she and Mel are being married in a formal wedding. Kara has asked our brother to walk her down the aisle, but he has reservations about the wisdom of her decision. He feels his sister has crossed the line.

The wedding is set for June. Charlotte refuses to allow her sons to take part in the ceremony. She plans to take them to Florida that week.

Abby, do you think it is wrong for Kara to marry Charlotte's ex-husband? -- BIG SISTER SUE

DEAR BIG SISTER SUE: What I think about the propriety of this forthcoming union is immaterial.

What I am having trouble understanding is why Mel, whose marriage to Charlotte ended because she cheated on him, would want to marry another woman who cheated on her husband.

DEAR ABBY: I am a 25-year-old woman who is dating a 47-year-old man I'll call Roy. My problem is I don't know how to break it to him that I am no longer interested. It seems to me our relationship is based solely on sex.

Roy tells me all the time how much he loves me, but I think it's the sex he loves. From my perspective, we really don't have anything in common.

He is currently separated from his wife and has a 16-year-old daughter who doesn't know about me. Roy lives in another state, but we see each other often.

Last week he told me that when his divorce is final, he wants to marry me. I was OK with it until I did some serious thinking. Roy asked me if I had a problem with his age, and I said no -- although the fact that he's old enough to be my father does bother me.

I don't know what to do, Abby. If I break it off with him, he's not going to take it well -- I just know it. But if I let our relationship continue, I'll feel like I'm leading him on. He's talking about relocating to be with me. How should I handle this mess? -- TRAPPED IN NEW ORLEANS

DEAR TRAPPED: Don't feel guilty -- just be honest. His age DOES matter to you. Level with him before he further disrupts his life to be with you. He may not take it well, but it's better than his giving up a job and relocating, only to be disappointed later.

DEAR ABBY: I finally figured out why women live an average seven years longer than men. They don't have wives. -- DIVORCED IN DENVER

DEAR DIVORCED: Not so fast! It could also be because they don't have husbands.

What teens need to know about sex, drugs, AIDS and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-sized, self-addressed envelope, plus check or money order for $5 (U.S. funds) to: Dear Abby -- Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in the price.)

DEAR ABBY: I have been dating "Jay" for four months. When I met him, he gave me his cell phone number. He said he doesn't have a home phone.

He won't tell me where he lives because his "ex-woman" stalks him, is dangerous, and he doesn't want her to cause me any problems. He says she has access to his apartment. (The apartment is in her name.)

I care a lot for Jay and don't want to lose him. He has keys to my house and knows my home and work numbers. I've kept no secrets from him, but I suspect he is still involved in a relationship, and that's why he doesn't want me to know where he lives. Should I continue to trust Jay, or do you think he is deceiving me? -- FEELING HURT IN THE NORTHWEST

DEAR FEELING HURT: I think he's deceiving you. Everything you have written about him indicates he's still involved with someone else and probably living with her. My advice is to change your locks and home phone number, and if he calls you at work, be unavailable.

DEAR ABBY: I am a 30-year-old female and have been repairing computers for two years. I thoroughly enjoy it. However, the field is dominated by men, and I have a problem.

My boss doesn't take me seriously. He will put a malfunctioning computer in front of me; I will test it and tell him what I think is wrong with it. Abby, he always disagrees with me.

When he puts the same computer in front of one of his male techs and they will tell him the same thing, he always agrees with them.

I think it's time he gave me credit where credit is due. Is there anything I can do to change my boss's behavior, or should I consider moving on? -- FRUSTRATED GEORGIA TECH

DEAR FRUSTRATED: You're not going to change a member of the old boys' club. Consider moving on, but not until you've found something equally good or better. Now that you have experience, I'm sure there are plenty of job opportunities for a tech with your diagnostic skills.

DEAR ABBY: I have been married to "Gerald" for more than 50 years. He is a wonderful husband and a splendid father. He still showers me with affection: kisses me good morning and good night, calls me from the office at least once a day, is a great provider, never argues about money -- essentially I can do anything I want. In addition, Gerald is an attentive and highly competent lover.

Throughout the year, Gerald gives me presents -- flowers, candy, things for the house, etc. However, he never gives me presents for my birthday, our anniversary or Hanukkah. I receive only a card and a hug.

I don't like it, Abby. When I tell him how I feel, he just smiles, gives me a hug and a kiss, and says, "Honey, that's not my thing." Nothing I say or do convinces him to change. Any suggestions? -- PATRICIA IN SAN FRANCISCO

DEAR PATRICIA: If after 50 years of marriage this is his only fault, consider yourself a very lucky woman. Develop a sense of humor. Go shopping for holiday gifts for yourself. Show them to him and say, "This is from you. Thanks, Honey."

Abby shares more than 100 of her favorite recipes in two booklets: "Abby's Favorite Recipes" and "More Favorite Recipes by Dear Abby." Send a business-size, self-addressed envelope, plus check or money order for $10 (U.S. funds)

to: Dear Abby -- Cookbooklet Set, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in price.)

DEAR ABBY: You were a little rough on "Tom" in your reply to "The Office Gang," the letter about the female trucker who kept coming on to the only man in the office. You implied he was like a little boy who lacked courage. I must disagree with you. Take it from one who knows: I've been in Tom's predicament more than once.

In the workplace when a woman is interested in a man, she usually lets him know discreetly. They can then proceed with a relationship if they're both interested, or quietly let it go. Then there's the occasional woman who won't take no for an answer. What starts as a nice ego boost can turn unpleasant in a hurry.

We men are taught from an early age to respect women and not show aggression toward them. Persistent females who show sexual aggression when we're not interested present males with a real problem.

I think Tom is trying his best to defuse a delicate situation. He wants this woman to back off, but he also wants to be polite and not cause problems for himself, the woman or his co-workers. He is not being a coward, Abby -- he's trying to handle the situation with the least amount of fallout. Give the guy a break, huh? -- BEEN THERE IN ALABAMA

DEAR BEEN THERE: If I gave the impression that I thought the man was a "wuss," I apologize. However, an aggressive woman with romance on her mind is not likely to give up if the target of her affection sits there and says nothing. Read on:

DEAR ABBY: I loved the story about the female truck driver who couldn't keep her hands off the only man in the office. I had the same experience.

During World War II, I worked for a wholesale company, and my department handled government business. The woman in charge of sorting the mail would put mine aside so she could deliver it personally.

There were four women in my department, and the mail sorter would wait until they were away from their desks to bring my mail to me. She would slowly bend over my shoulder from behind and plop one of her breasts on my shoulder while she kissed my ear!

This routine went on for some time, until I finally discussed it with my staff. They devised a plan: They had me take off my coat, then they stuck straight pins up through the shoulder pads. When they thought it was time for this gal to deliver my mail, they all trooped off to the washroom.

Sure enough, she sneaked up behind me, slowly bent over and -- plop (ouch!). Abby, she never did it again.

Of course, the ladies were watching what went on from the washroom. When they finally returned, their faces were flushed from laughing. -- ART ROLLINS, PORTLAND, ORE.

DEAR ART: You got your point across. I'll bet she was sorry she tried to make a boob out of you.

DEAR ABBY: My older brother is being married at the end of May. He has asked me to be his best man. What are the guidelines for giving a "best man speech"? -- I WANT TO BE THE BEST BEST MAN

DEAR BEST MAN: It should be a short state of the union speech. Save the inside jokes and naughty comments for the bachelor party. At the wedding, congratulate the couple, offer a couple of G-rated compliments, raise your glass, and wish them a lifetime of happiness together.

To receive a collection of Abby's most memorable -- and most frequently requested -- poems and essays, send a business-sized, self-addressed envelope, plus check or money order for $5 (U.S. funds) to: Dear Abby -- Keepers Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in the price.)