Partnered Sims turn into siblings

So I play on Xbox series S, I have all the packs and kits for the game and in my longest save file I have 3 spell-casters who are all romantic partners and for some reason they have become sisters when their not even related by blood. I can’t do any romantic interactions with them only serenade and give massage and it has me very upset. I also have lovestruck so the romance bar right now is full but with that pack it’ll eventually dwindle down eventually and I won’t be able to do anything to restore their romantic relationships with each other. If there are any fixes for this it’ll really be appreciated. Btw I don’t play with mods at all so I can’t use MCC or anything else other than normal cheats for the game. I tried using the cheat: cas.fulleditmode to switch them back but it was unsuccessful. They even have a label in their sim profile that says they’re all sisters and that’s just incorrect. Please help ! This is my longest save file I’ve had since I started playing and I don’t wanna have to resort to drastic measures and mess up my family tree. 

For clarification, Hope Brignoni, Jacquelyn Black and Etta Bishop are in a polygamous relationship (even though there are none in the sims 4, but I was using my imagination) and they’re not supposed to be sisters, they’re supposed to be romantic partners. I attached photos of the labels, household relationships and the family tree and how they state their sisters. Mind you my sim Hope Brignoni is a descendant of the first ever sims I made of me and my husband. I’ve been playing this save game for 10+ years. I’m on generation 8. Please help ! 😩