A few minutes into playing after updating, my sim gets a call from her cousin to say that the cousin is now in a relationship with her own brother. I went into the other family to check and sure enough they have a romance bar, and are tagged siblings, sweethearts, and partners. This is NOT okay.
Edit By crinrict: Adjusted Title to fit old bug report.
something similar happened to my game a while back. i noticed the issue in the family tree first:
somehow - my sim (Bella of all people) became the daughter of one of my other sims. they were already married for... forever practically. it just happened one day.
just tried to merge the family and edit the household relationship, so her faux father was a household member. it was not possible. i was given the option in fulleditmode to select household member instead of father, but when i clicked on household member it doesnt switch. it just goes back to father.
tried to do the same thing with my sims husbands mother so she's no longer my sims sister - and same thing. it will let me edit other members in the house - but not the one thats the problem
It is absolutely mindboggling and annoying and frustrating that I have completely reinstalled the bloody game, started a completely new game and it happened again. It seems to be happening every time my sims have more than 2 children and I go in CAS to change anyone's appearance. I'm just done with this game. It costs so much money and they cannot even fix this damned issue.