Dear Prudence is Slate’s advice column. Submit questions here.

Dear Prudence,

My sister’s son is a couple of months older than my daughter. He’s always been slightly off.

But over the past year or so he has become overtly threatening toward her, with crude comments that make her very uncomfortable and sexualized social media posts about her. I’ve had very strong words with my sister about this behavior and have made it clear that I will not have my child in the same room as hers, which, quite naturally, has caused a massive feud that is spilling over into our entire family. My parents are up in arms, everyone is taking sides, and I am looking for a strategy for navigating all of this.

For now, when somebody raises the issue, I just share a screenshot of some of my nephew’s more troubling comments and say this is not something I am prepared to discuss. I’ve also advised my daughter to block her cousin on all social media and have built a large folder of his posts, which I am seriously considering passing on to the police. I just don’t see an option that isn’t nuclear.

—Not Having It

Dear Not Having It,

I Left My 2-Year-Old Alone With My Husband for 15 Minutes. The Aftermath Might Haunt My Marriage Forever. Help! My Mother Has Some Strange Ideas About Underwear That Are Causing a Major Mess in My House. This Has to Stop. Help! I Found the Handkerchief My Mother-in-Law Was Using for a Really Offensive Test. This Content is Available for Slate Plus members only When My Son Came Back From Easter at His Dad’s, He Was Counting a Stack of Money. I’m Stunned by How My Ex Let Him Earn It.

You’re handling this exactly right, and I’m so glad you’re standing up for your daughter. I’m not sure the police will be able to do much about the sexualized posts, but if your nephew has really threatened her, that’s something you’ll definitely want to include in a report.

The only other thing I’d suggest—and I say this knowing the situation may have already escalated too much for it to be a realistic option—would be for you to encourage your sister to get some help for her son. What he’s doing isn’t normal, and it suggests that he may be struggling with having been victimized in some way himself, or with mental health issues that he can’t manage on his own. If you can’t speak directly to her, spread the word to the family and hopefully someone will mention it to her. Your statement that he’s “always been slightly off” makes me think it would be worth it to do some digging to get to the root of his behavior.

I’m sure you’re already thinking along these lines, but please make sure your daughter knows that even if the whole family falls apart over how to respond to what she’s dealing with, it’s not her fault, and that protecting her safety is absolutely worth it.

Classic Prudie

I live with my aging and ailing father. He recently invited his old college roommate to visit and discuss doing some renovations on our home (his friend is a contractor). I found him to be a pleasant enough man, but grew concerned after a couple of days over a strange—and disgusting—habit I noticed.