DEAR ABBY: About 20 years ago, my mother-in-law confided something shocking to me.

Some background: My husband has two sisters. One is a year older and looks just like him. They both resemble their dad. The younger one looks nothing like the other two or their dad.

My MIL told me she and her husband stopped having sex after my husband was born. When I asked, “What about the younger sister?” she said she made a “mistake” with someone. We talked, and I suggested how important it was to tell the kids about this, but she never did. She always told people the younger one looked so different because she was so many years younger than the other two.

Both of my in-laws have passed away now. Why did she tell me this? She was too much of a coward to tell her kids. Did she think I’d tell them? Knowing this really bothers me, but I still can’t bring myself to tell them. It would change their lives and crush them. Any advice would help so much. — WISH I DIDN’T KNOW

DEAR WISH: Your sister-in-law deserves to know the truth. Tell her privately, in circumstances where you can talk this through. Explain that you have kept this secret because it was her mother’s wish, and you don’t plan on sharing the information with anyone else.

She may have quietly wondered for years why she didn’t resemble the rest of the family. She may or may not wish to tell her siblings, but she should be free to handle this any way she chooses. Because you are all mature adults, this information should not crush them.

DEAR ABBY: I am a senior woman who never married or had children. I met a senior man, “Warren,” on an online dating site, and we have been dating for a year and a half. It’s a platonic relationship; we go out twice a week. I have slept over but always in separate bedrooms. We are good friends.

My sister is selling her house. I have lived with her for 32 years and I pay rent. She wants me to move out in a year. I’m on Social Security and can’t afford an apartment, and government aid is not promising. Warren asked me to move in with him to help each other out. He will rent me a bedroom. My sister and a friend of mine are against it. Their concern is he wants a live-in maid, and if it doesn’t work out, where would I go?

Having no other choice, I’m seriously thinking of moving in with Warren. I really like him. He’s a very nice companion and treats me well. Should I listen to my sister and friend and try harder to find a place to live? — IN LIMBO IN FLORIDA

DEAR IN LIMBO: Talk to Warren and find out what, if anything, he will need from you besides rent if you take him up on his offer. You might want to draw up an agreement with him in writing so there are no misunderstandings later.

You didn’t mention if the rent you will be paying is as high as what you have been paying your sister. If it isn’t, consider banking the difference so you will have a little more independence if things don’t work out. From what you have told me, the arrangement you are considering could be rewarding for everyone involved.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Contact Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.