Partnered Sims turn into siblings

With the recent update, some of my Sims that were previously married and even have several children together are now listed as siblings! Because of this, they can't create more children, and their biological children are also listed incorrectly as their nieces and nephews. When I look at some of these children's family trees to see who is listed (incorrectly) as their biological parents, it shows relationships that are also impossible like two fathers, one of which is dead anyways and never knew the other sim listed as the second father! I have tried to go into CAS to fix these relationships, and I saw that there was still (seemingly) the option to change one of the relationships from sibling to a household member. I tried to select household member (with the intent to just start over and remarry this couple) and it wouldn't let me select this option, forcing me to keep them as siblings. This was not a problem until the most recent update (I also have zero mods installed).