Strangely, this even happens to Sims that are happily married. So, after installing the update, you may find that your Sim wants to date their brother or parent. Unfortunately, there was an issue with the implementation, and the game generated Wants without regard to familial relationship, marital status, or sexual orientation. Each Sim has a number of goals they want to achieve and things they want to avoid. This update replaced Whims with a feature similar to the one found in The Sims 2. The issue stems from the Wants and Fears system that EA added in the July patch.

Fortunately, the bug causing Sims to want to enter a relationship with their family members doesn’t mean they actually can. While there are mods that add incest to The Sims 4, making WooHoo with your family is typically a big no-no in the base game.