Partnered Sims turn into siblings

Did you upload them ? What's the name of the family ?

My married sims randomly turned into sisters and I can't change it either

Sorry just got home, the family is Jayvik I just shared it to the gallery 

I've been playing with two married sims for a while now — they even have two children together. But somehow the game glitched and made them siblings? No clue how that happened. I tried removing the relationship bits using shift + click cheats and playing vanilla, but nothing has helped. 

One of the married sims is an elder so I can't create parents for them, but the other sim has a mom in the game (I've been playing with the second sim since they were a child). 

Has anyone else had this issue? If so, how did you fix it (or were you able to fix it)?

Thanks. Wasn't sure from your post if I'm just not seeing them :D

Checking them out now and let you know.

Hi xXPaintedLadyXx​ 

I checked your family and they have indeed the sibling issue.

Going to merge this with the main thread

How I tested and bypassed this bug. I first tried swapping out one of the partners with a copy, but the bug returned when I went to CAS. Then I swapped out both partners and their one child in the household with copies I had in my library, and aged the child back to prior to their birthday (the birthday and trip to CAS was about when the bug occurred for me), and placed them in a clean save with no mods. I aged the child up there, and no bug occurred. So I went back to the original modded save, with the new copied family and the child aged back prior to the birthday, and aged them up again and no bug occurred. So I would suggest that if you have a copies in your library that may be the only way around this bug, but obviously that's not a great solution since you will lose relationships and maybe progress if it is not a recent copy. This bug is very tenacious and hard to work around and a real solution is needed.

wtf sims 😟can I fix it?

Also experiencing this issue on PC. It's not mod related as far as I can tell. I think it started when I went into CAS to check something. I came out and all of a sudden my legacy heir of like ten generations can't do any romantic interactions with her wife. I'd heard about this issue yesterday so I checked to see if they were suddenly siblings, and indeed it's the case. I've tried resetting their relationship with MCCC to no avail. I really don't want to move them to a new save because I don't want to lose my progress with their business... I'll keep trying different things and if anything works I'll come back and reply.

Ok, I tried a lot of cheaty stuff and I wasn't able to fix it, so I did have to make fresh copies of the Sims. Here's what I did:

1. Saved my family in their current state to my library.
2. Copied the family to three separate empty lots in Newcrest.
3. In one of the lots, I deleted all but one of the problem Sims and created dummy parents for her. 
4. I repeated for the other problem Sim on a different lot.
5. In the third lot, I deleted everyone but their kid.
6. I made the fresh copies of my problem Sims meet, cheated their friendship and romantic relationships to maximum, and had them get married.
7. I split them into their own household, and then I merged it with the one that just has their kid. 
8. With CAS full edit mode, I set their kid's relationship.
9. I evicted the glitched version of the household and replaced it with the one I just created in Newcrest.
10. Finally, I had to create their family business again and cheat it to where it was. 

I think this way is better than some of the other ones I've seen suggested here because it'll save all your Sims' traits and milestones and even aspiration progress and you don't have to find a backup version. As far as I can tell, it's working okay and it hasn't come back yet.

I don't think this glitch was caused by the fact that one of them didn't have parents in game, but based on some of the other posts in here I do suspect that it did allow it to happen. Regardless, this was a huge pain to solve and was actually devastating to me to discover the glitch so I really hope they fix whatever's causing this soon.