Partnered Sims turn into siblings

After my two sims, who had been married for a while (and obviously not previously related), adopted a child, they no longer had a romantic interaction category. I went to check why that was, and it turns out they were now related. I have McCommand Center and UI cheats and tried to cheat away the relationship in every way possible to no avail. Doing this removed the sibling relationship, but it was promptly replaced by a new cousin relationship. After trying to remove that one as well, it just flip-flopped between the two. I also removed my mods folder to see if it was a mod issue and gave it a try, still didn't work. In CAS, the option to change the relationship was greyed out, despite cas.fulleditmode being turned on. I searched for any solutions, and it turned out this has been a problem for years and it seems the only solution people have found was to delete one parent and add them back with the gallery through CAS. I have spent a lot of time developing these Sims and have no desire to attempt that solution, so please help. I beg.

Right now I'm having this same problem, last night my game was completely normal, my sims were kissing, flirting and just being romantic with eachother like they normally do, I got a couple of mods but they were working just fine. Something makes me think that the problem started when I accidentally aged up one of them, I made her a young adult back again and continued playing. I don't really remember if that's where the bug started, but I've seen a lot of people saying the problem started after they used cas.

I tried using cas to change their relationship but it doens't work, mccc and other mods also don't help and deleting them didn't do anything. I don't want to have to start from scratch with these sims because they already have a beautiful family, I don't want to and can't sacrifice that.

This is happening to me too!! Also on separate occasions, I’ve been my legacy for 10+ generations and don’t want loose all my progress because of this bug… is there any solution yet??? I’ve tried using MCCC to fix it but it always goes back whenever I change lots. 

happening to me on ps5 right now — it’s literally unfixable in CAS with cheats. 

I had to move both partners out (so there is room in the household. 
delete partners relationship (using MCC) Enter CAS and create two random elders. It was letting me connect only one of the two to partner 1, so I left CAS and used MCC to assign the other parent to partner 1.

Delete relationships for partners again. Also may need to delete relationship from partner 2 and partner 1s parents you just made. Go back in CAS and do the same thing with partner 2 and assigning to random parents to them. 

Basically, you need to create 2 parents for each partner and will likely need to keep deleting relationships whenever anything is adjusted to ensure the sibling thing doesn’t come back. After I had to parents for each, it finally fixed itself. 

In then reintroduced them. After that, I cheated their friendship and romantic relationships back to max

Playing on a Mac and now having this issue with a lesbian couple I was playing that has 4 children. The only romance option I had was to offer a massage. I am not quite sure what caused it but it started around the July 10th patch. I had used the cheat cas.fulleditmode to fix something with one of my sims and didn't notice the issue until a few hours later after I had already saved a few times over so I couldn't recover an old save. I don't want to download the MCC mod since I prefer playing a clean game so I tried to create separate parents for the sims; I tried moving them to different lots; I even tried killing one of the sims off and having her be reborn (I have the Life and Death pack) to try and fix it but no matter what they still view each other as siblings. All their romantic satisfaction went away which was such a bummer because I have been playing this couple for months. I ended up moving an old copy of one of the spouses from the gallery and basically just pretending like she's the same Sim but it stinks because she doesn't recognize her kids as her own since all her relationships/memories/skills are gone. Please find a fix for this bug soon!! 😭

I’ve just had this bug! I’m on console. Is there anyway to solve it :(

ruining my legacy!

I am aware this has been a previous issue but it’s happening again….  and this time it’s on console! I don’t know if there is a way to fix this on console but it’s now ruining my legacy challenge 

I have two sims that were/are dating, they have one kid together and now when I open the game every time I go into CAS, (and even when I don’t open CAS it eventually happens), CAS just always causes it no matter what,) they become sisters and can’t preform romantic interactions aside from a massage. I played without cc or mods and this is still a problem. Idk how to fix it and using cheats or mods such as MCCC doesn’t work. I’ve tried moving them in separate households and everything but even in separate households once the one sim goes into CAS it sets them as sisters once again. I have noticed it’s only when that once sim goes into CAS though. The other one can do that same thing and they don’t become sisters. But now the game save is ruined and their son is the non-broken sims nephew and it’s really annoying. I’ve seen people complaining of this happening as long as 7 years ago but I just had this happen after the last big update that broke pregnancy and everything. (I’m on a windows PC)

I have a romantic couple that just today started showing as brothers and can't do any romantic interactions except under the relationship option they can talk about their relationship or seek therapy. No mods. PC. All packs and most of the kits installed. They were doing the enchanted by nature event after I downloaded the fairy pack and the patch after it. They were fine a week or so ago when I was working on the event with them. I think they're the only household I've played during this time.