Dear Amy: After many years of marriage and two children, my now ex-husband revealed that a few years before he and I met, when he was about 30, he had a "consensual" sexual relationship with a 15-year-old, non-biological relative.

I was devastated by this information and, in light of other serious problems in our marriage, we divorced.

We've been divorced for seven years. Our children are 15 and 17. My ex and I share custody of them. I haven't told our kids — or my family — about this event.

I'm living in fear that my kids will find out one day and that they will resent me. Holding onto this secret has cost me a price, personally. On occasion I look like the "bad guy" in our divorce, which is unfair to me.

Should I just live with this and hope for the best?

Amy says: First of all, no sexual relationship with a 15-year-old can be considered "consensual," because (with a few exceptions depending on the state where this occurred) 15-year-olds are too young to consent.

The age differential between a 30-year-old and a 15-year-old makes this lack of consent more obvious (this is not like two teenagers having a sexual relationship).

If you have any valid reason to suspect that this behavior might continue (or resurface), then you should notify your children. But you don't mention having this concern.

You have every right to loathe your ex for this sexual misconduct. You don't have the right to use your knowledge of this to retaliate against him. And so you have to question your motivation.

Based on the way you've framed this, you seem worried that your kids might have too high an opinion of their father — when you believe that he doesn't deserve it. But he is their father. Familial love is not balanced. Children do love undeserving parents.

If your ex lies to your children about you or unfairly casts you as "the bad guy," you should immediately correct the record. Otherwise, this is not your secret. It's his. If the victim ever chooses to come forward, he will be forced to face this.

You worry that if you don't tell your children, they will resent you. I believe it's more likely that they will resent you if you do tell them, because you would be transferring the burden of this knowledge from yourself to them.

Losing weight or money?

Dear Amy: I recently saw a friend for the first time in six months. In the interval, she had lost a lot of weight, looked great and obviously was feeling amazing.

I asked her how she'd done it (we often discuss diets), and she named a weight-loss program I'd never heard of. She said she would email me details and was enthusiastic about me joining this program.

When I got home, I looked up the name of the program she'd mentioned, and I saw that it is a multi-tier marketing scheme. It appears to be quite expensive, and the program urges members to recruit new members.

I'm not planning to participate, but I'm torn now about telling my friend about this scheme. I'm also wondering how to turn her down when she contacts me. Any ideas?

Amy says: Assuming that the information you gathered is correct, the way to turn down an offer to join a multilevel marketing scheme is: politely, firmly, and — if necessary — repeatedly. You can say, "I'm happy you're doing so well, but this is not for me."

Send questions to Amy Dickinson at askamy@amydickinson.com.