Not incest but close enough

Unfortunately I've had this too with a step parent. I turned off romantic calls and invites in my Game Options and felt thoroughly creeped out. The household was created with a Mother, her husband and her teen and YA daughters from a previous relationship. The teen lived with her mother and Stepdad, I used the relationship label to label him Stepfather and used the Adopt as Care Dependent social interaction. She then aged up to YA and left for University which is when he randomly invited her out. I have Lovestruck and I don't know if that affects it. She didn't have a high friendship bar with him and her storyline was that she didn't get on so well with him but they weren't enemies, just acquaintances.

I've had a look through the bug reports because I thought it might be one but couldn't find a report. So maybe feedback for now.

Unfortunately people have been complaining about this for years. They'd rather work on the next expansion pack than fix it. I was playing a family of immortal spellcasters and my sim's great uncles kept getting negative sentiments towards her because she was rejecting them. Step parents will hit on their step kids. The only way to fix it is mods.

I'm just playing a Step Parent again and I noticed that this time she got 2 options regarding Adoption. She could Adopt her new husband's son fully as soon as they moved in and even before they got married, or she could Adopt as Care Dependent. I chose Adopt and she is now listed as his Mother. I've created this household before and last time she just Adopted as Care Dependent as that was the only option and she wasn't listed as his Mother. So this option might stop any future inappropriate interactions 🤞.

I think maybe that did not show up for me because I had the wife and two husbands. The game allowed this to happen through use of a NAP but I don't think both marriages really counted. I did use the care dependent option but once she became a young adult I don't think that counted for anything any longer. Hence the problem :(

I do use mccc mod but haven't seen anything I figure to be useful for this in there. So I had to use ModifyRelationship Sim1 Name Sim2 Name -100 LTR_Romance_Main and do them down to a full red romance bar and then make it +100 to put it to an empty romance bar. This changes them to just good friends but I don't trust it. I have searched and searched and can't find any way to get rid of the romance bar entirely unless I want to just make them forget each other totally. I am playing the now young adult sim household right now and she is married and they are working on careers. She is friends with Bella Goth and Bella showed up at her door wanting to give them a neighborly present (even though she is not a neighbor) and I noticed when I highlighted Bella that she was a romantic interest. WTH?!? There has not been an opportunity for anything like this to occur and I'm really getting tired of it. I also noticed in relationships that her grandparents were romantic interests and a couple other people. This is totally bizarre and I can only think of one explanation for it. "Social Bunny". My sim and her husband used it a lot while dating and living together. Because social bunny does help with relationships I have noticed. It's why I get the random notifications that my sims became good friends with people. And I thought it would be like social apps I am used to and you can like, not like or love posts or blow a kiss to show you care. I am convinced that somehow the love eyes emoji and the blow a kiss emoji are what caused these relationships to become romantic interests. Nothing else makes sense. So I have stopped using those emojis and will see if that solves the problem. I will post again about it if it does not. 

Meanwhile, I still have these romance bars that even though they are just good friends, it will only take one slip up of my not noticing and her relationship gets wrecked. So if anyone knows a way to get rid of the romance bar without making them forget their whole history, I would sure appreciate knowing. Thanks!

Yep. Very close to, if not exactly, what I am experiencing. The adopt as care dependent does nothing once they age up. It is just too creepy. Since I didn't realize all of this might be an issue down the road, I didn't really pay attention to some things I might have. I will next time and post back if I can find a solution. Maybe I caused it with the social bunny thing as I explained above. So I can't say for sure it would have happened if I didn't use the social bunny. Do you remember if you did and ever used one of the heart emojis to the stepdad thinking it was innocent?

There is a mod by Lumpinou that lets you disable romance for family and has extended family tracking. It takes a little setting up and you'll have to download a few extra mods from her to make it work, but it's from her RPO collection.

Here's the full title of the mod if you wanna search it up. I believe you'll also need M0 and her toolbox, but double check to be sure.

[Mod] RPO Collection M20-21 part 1: Auto Bio Family Tracking + Auto step / in-law family tracking - Sims 4

Nightgypsy​  I detest Social Bunny so I don't use it unless I'm playing certain teen Sims. It makes no sense at all that they get random insults from good friends. So I avoid. I'm on Xbox Series X so I don't use mods. The empty romance bar really annoys me, it's a reminder of the ick! But I keep a backup save and I've been able to switch to that before after unwanted incidents of inappropriateness.

The Bella Goth incident makes me wonder if it's mod related 🤔. On here the advice is always to test without mods to see if the problem persists. We have excellent mod support here:

The Sims 4 Mods & Custom Content | EA Forums

Yeah I will remove my mods if the issue returns. So far so good though. I feel the same about the random insults and keep thinking is it just me and that is supposed to be a funny somehow. I think I was only bothering with it because there is an aspiration in which part if it wants you to have 250 followers on social bunny. My sim has far surpassed that but I been working on a different aspiration and haven't switched over to it. I guess I will to get it done and then close out the app lol. 

Thank you. This sounds interesting and I will check it out. I really only use Mccc and mods from LittleMsSam. Once I get my game files moved to where they should be and properly backed up I might pick this one up :)