Sibiling relationship bit being added

Whenever I go into CAS to modify appearance or outfits, my Sims who are in a romantic relationship will have a sibling relationship bit added. Using MC Command Center (yes, I do use mods) to remove the bit does not fix it as they still cannot perform romance interactions on each other. I have tried removing the bit, and then saving and closing my game, and deleting the cache but it just comes right back upon reload. This happened before the July 1st 2025 update, but is still persisting. It has made one of my saves unplayable.