Sim cheats with step-son? Is this a bug?

So, my sims can't stop cheating on each other. The loyal sim seems to be the worst, but they're all pretty equal here. The worst part is when my sim, who raised a boy since he was an infant to adulthood and was the caretaker for (married to his mother), started flirting with his step-son?

This is constant. I can't keep certain sims in the same room for longer than 1 gameplay minute. It's exhausting. I used to never have this issue before? I will literally have a couple flirting with each other, and another sim comes up and tries to flirt with one of them???? 90% of my gameplay time goes to mending broken relationships, what in the world did this update do to the game?!

I have CAS mods, but no script or build mods. I have all packs except certain kits. My household includes 2 humans, 1 servo, and 3 occult sims (2 vamps, 1 ghost).

Does anyone else have this issue?