Partnered Sims turn into siblings

My sims couple are now marked as siblings. 

Apparently this ONLY happens to same-sex couples who have adopted (?!) and has been a thing since early Feb... And I feel like I've tried everything. 

But because they are showing up in the family tree now as having the same parents (even though one of the two sims is created by EA and came with Lovestruck and had no pre-made parents), nothing works.

I've tried removing the relationship with MCCC, removing them as siblings in MCCC (there's no option to do this) creating separate parents for the Lovestruck sim (which DID do something... It made the couple COUSINS)... Deleting the sims from the household and re-placing them into the family from my Library, changing the relationship in CAS full edit mode (it's greyed out)... But the sibling (or cousin) relationship will not budge. 

Is there anything that works that I haven't tried (that doesn't involve starting over, deleting and re-adding them, or using MCCC?!) I've played this save for years and am generations in. I don't want to have to wipe it clean!