Partnered Sims turn into siblings

My sim, her husband, and her other partner have all become half siblings. I tried to fix it in cas with the cas.fulleditmode turned on, but it wouldn't let me change it. Only one of them allowed me to put the relationship as partner. When I clicked the 'household member' option for the other, since spouse did was not an option, it remained brother.

They are still married in game while being half siblings, and before I managed to fix the one relationship they still had a child together. As far as I know half siblings are not able to have children or romantic relationships with each other.

This happened in another household I had played the other day as well. I fixed it by deleting the household, then redownloading it. I don't want to have to do that with every household though. It also happened to the mother of a sim in the first household I mentioned. She was suddenly not the parent of who was originally her son, and I could not add the dynamic.

I removed my mods, and the problem was not solved. I then repaired the game, and it still was not fixed. It started after downloading the Royalty and Legacy EP, but I'm not sure if there is any correlation.