Married Sims are tagged as siblings?

I noticed a recent bug where my married sims are now tagged as sisters, and I cannot change this. I've tried cas full edit mode but their relationship is tagged correctly in cas. I've used the UI cheats mod to try and cheat their relationship, but this isnt working either. They've been married for forever with 3 kids, and now their relationship is declining rapidly because they cant do anything romantic together :( I've troubleshooted by removing mods/cc, updating mods, repairing the game, updating the game, etc - but nothing has worked.