One of my heavily pregnant sims took her husband to the romance festival. Husband ran into his father-in-law and started autonomously flirting with him. His wife was so mad; she got her revenge by autonomously flirting with a random townie she never met again. To keep them from getting jealous, I decided to turn on the Free Love NAP. That ended up being a mistake, as the husband then would flirt with all of the male neighbors, including his wife's sister's husband. Once they had all the kids they were going to have, I let them divorce so he could go live his best life with his favorite neighbor.