When everyone said they wanted Sims to have more interesting lives, I don't think any of us meant incest. Nor did EA intend it, so a Sims 4 patch yesterday has addressed the sudden tendency for Sims to try pursuing a romance with their relations.
A few different bugs cropped up after the romance-focused Sims 4 Lovestruck expansion and a base game update last week but the two most prominent were Sims being way too mean to each other for no particular reason and Sims deciding to develop illicit relationships with their family members. It was happening through the "Neighborhood Stories" feature which allows Sims outside your played family to have life milestones of their own like marriages, pregnancies, job changes, or accidental deaths without your direction. Nice, in theory, if you want a more lively neighborhood developing around you that you don't have to micromanage.
It's less nice if your Sim's next door neighbor calls them up for some friendly advice about pursuing their crush and the crush is actually their sister. No, dear neighbor, please do not go for it. Somehow, this isn't nearly the first time that Sims have accidentally wanted to date their family members.
Your Sims should now be safe from bearing witness to forbidden crushes and, specific to the Lovestruck expansion "Sims no longer receive inappropriate phone calls from relatives," say The Sims 4 patch notes. This hotfix happened on Friday fr PC players and yesterday for consoles, so we should all be equally safe now.
If you've never messed with Neighborhood Stories, by the by, you can find them in the "Manage Households" menu by clicking that diverging arrows symbol and turn on individual autonomous changes you want other Sim families to be capable of. The "romance changes" toggle should now be safe to enable.
If you were leaving your EA app offline to avoid downloading the latest game update for fear of any new base game bugs that EA has recently announced it's recommitted to fixing, let this be your sign that the more troubling ones are tackled.