[NEEDS SAVES] Partnered Sims turn into siblings/family relationships

So weird. I tried the trick to destroy relationship and reset the relationship, but it didn't work. Even downloaded the MCCC mod to edit the relationships, but they never stuck.

However, I did figure out a work around: if you split household and move one of the spouses/partners out, then you can enter CAS without altering the relationship. Afterward, you just invite the spouse back over and Move them in. A bit of a hassle, but you don't lose any of your Sims progress or inventory. 

Thanks for looking into it!