Partnered Sims turn into siblings

Please fix this EA, I can’t enter Create-a-Sim without my same sex partners becoming siblings. They’ve been married for a long time and have two teen children. It makes it worse that this seems to be happening most frequently with same sex couples…

This has been an issue for me dating back over 3 years. Why is this something not being talked about enough? This is a huge immersion breaking issue. I haven’t played with my sims for years because of this issue. It’s been so hard to enjoy the game because I’m not attached to no other families. This needs to be addressed asap.

Started playing a legacy save a few months ago.  I play with only MCCC occasionally, but have played this save without mods for the last few weeks and I play with no CC. 

The couple in question are a same sex couple with one child, not a science baby or adopted, it's their child, and one of them has skillful sleep, which seems to be key, and don't think I'll let any future same sex couples have skillful sleep again.  Their child just aged up to teen, and shortly after I noticed that they no longer had any romance options.  Went into their relationship and it shows them as siblings, as well as married etc.  I had gone into CAS after their child aged up to fix various things, as we do, and I'm guessing that is when this happened.

Went looking in the forum here for an answer, only to find out this has been an issue for years, but also from reading through this thread, seems to have become a much bigger and more widespread issue in the last few months and yet it appears EA isn't even looking at this thread!

I am beyond annoyed and frustrated that this issue has persisted for so long, that it seems to affect only same sex sims and yet silence from EA.  I've tried EA's fixes with repairing and starting a new file and moving the save into it, but nope, it's still an issue.

EA you need to do better and actually look at this issue!  I want to be able to play sims representative of me, and you seem to want to make sure of the same from that recent survey, and yet when I play a same sex couples, which is representative of me, there is a major freaking glitch, that does not seem to affect opposite sex couples!  Do better!

Just in case it's helpful for figuring out the problem I've attached the link to my save file.

https://drive.google.com/file/d/1Wx5lN_5bQVn8frnR2PbuhlSixsdv2kVW/view?usp=sharing 

I'm not holding my breath but would appreciate hearing from someone that EA is actually looking into this issue, since it is so game breaking for so many people!!

This just happened to me for the first time! I have never played with any mods or CC - just the base game and EP's. It was my fairy couple and so at first I thought it was maybe something that happened due to fairy influence or something but obviously can see now it's been happening for awhile. Is there a cheat or something that can fix this? I've seen a few people mention some things but that the sibling relationship keeps returning. This is very bizarre and frustrating. 

This bug still exists.

I have two Sims who have been married for a long time, but I just discovered that they suddenly can’t perform any romantic interactions. Then I noticed that in their family tree, each of them suddenly has a “new” brother who doesn’t actually exist in the world. What’s more, this brother has the exact same name and appearance as their spouse.

Because of this, it seems the game now recognizes their spouse as their sibling.
And both "spouse" and "brother" are in "relationship".

Both Sims are spellcasters, and one of them did use Duplicato.
I tried repairing the save and rolled back to a state before the bug happened.

I found out what triggers the bug (at least in my case): entering CAS mode and then clicking “Save” (the checkmark button) — it happens regardless of whether I actually change the outfit or not.

This has 2 parts - my same sex couple sims were fine then suddenly in the relationship profile are now sisters - i tried reloading, clearing cache, repairing game, downloading MCCC and deleted the relationship and used cheats to get relations ship friendship and romance back to 100% - NO romantic options were available after this and I couldn't add relationship to partner or spouse in MCCC. Go into CAS on full edit mode and the relationship is set back to spouse!!!!! I got so frustrated I ended up deleting one sim (my sims spouse was off the gallery so no attachment) and on a separate note my sim is female and cannot pee standing up and is now using the toilet standing up!!! what the hell is wrong with this game!

I have that problem too and it's annoying. Why they can't fix that??? My whole family gameplay is destroyed. They get money for making the game work but they don't get anything fixed. I don't want to play incest families..

i have the same problem. a same-sex married couple suddenly became brothers — i suspect it happened after having their second science baby, everything was fine for a long time.

the worst part is that there’s no way to fix it — i tried removing their siblings status via mccc and via ui cheats extension, after anything that involves a loading screen they become brothers again. their relationships cannot be changed in cas. i tried saving the family to gallery, deleting one of these sims in game and adding him back — everything’s fine, not brothers, then i used mccc to again make him a husband (still fine), then reloaded the game — right after that they’re brothers again.

i gave up and unfortunately had to get a mod to force the game to ignore that they’re siblings to continue playing since it’s my main family in my main save.

upd: okay i got curious and decided to experiment a bit with it, so i saved my family to the gallery and started a new save only with mccc. i tried both adding them as one family straight from the gallery on world map and adding them by entering cas, choosing the family in the gallery and saving — the game showed them as husbands and brothers at the same time in both cases. so, i tried adding each of my sims separately in different households so there were no connections between them, then i joined the households and got them married (at this point not brothers, only husbands), saved the game and entered cas with cas.fulleditmode, then left it using X, not checkmark button — boom, they’re husbands and brothers. then i loaded the save i’d made before entering cas — they’re already marked as brothers. so for me any loading screen would result in changes in their relationships. i removed the siblings relationships between them in mccc and tried adding different parents to each of them in cas — the game wouldn’t let me add parents to one of them as if he already had parents, like it wasn’t even an option is cas, so for him i just created two sims and assigned them as parents using mccc. after that, when both of them had a separate set of parents, they wouldn’t get marked as brothers no matter what — leaving cas using X, using checkmark button, reloading, adding a science baby — everything’s fine. as soon as i removed one set of parents they got marked as brothers again, but the remaining set of parents doesn’t see the orphaned sim as their son.

so, basically, the only way i’ve found to avoid this bug is to manually remove the siblings statuses and manually assign two parents to each of them using mccc, because the game itself doesn’t let you do this, and keep these parents in the game.

(another curious thing i’ve noticed during this — if i remove their siblings statuses and enter cas, i cannot create a child for both of them using genetics, the game doesn’t allow selecting the second sim as another parent, so they in fact get marked as brothers again during loading, not after leaving cas, although in cas the game shows they’re first of all spouses, not siblings)

This is still happening. Are they looking into it?

The only way I know to avoid it is to always create two parents for your same-sex couples. 

I have the same problem. It is only linked to one sim. If I open CAS in ANY mode (i.e., with or without the cheat cas.fulleditmode on) while this sim is in the household, I will exit CAS to have my two married sims thinking they are sisters, and the only romance option is "offer massage". This even happens if I move the offending sim into another household - if I open any CAS with her in the household, even when her spouse isn't in that household, she will think her spouse is also her sister and refuse to be romantic with her, though she still has her listed as her spouse. I've never come across this issue before, it's so sad I cannot edit this sim! 
I have MCCC and UI cheats as my only mods, but from the sound of other peoples' comments this doesn't appear to be a mod issue, as it affects console players as well.