I wanted to make this mod myself but I don't know how to and the tutorials confused me. Basically I wanted to add some realism in the sense that family members bicker all the time and it doesn't mean they like each other less afterwards. Does anyone know of a mod that enables something like this?

They only lose friendship if their relationship drops below 50. If the relationship is that low, they should lose the friendship, IMO.

I think it's personality based, too. I think mean/grouchy sims like to argue, for example, and sometimes their relationship points increase after arguing.
Cyjon's Argue Social Fix for example, seems to mention that this happens.

That might be a good place to start looking on how to make such a mod, since you want to do the opposite of the fix, eleanordunkin. Otherwise, you would need to edit the socials you want (Argue, Irritate, etc.) to improve relationship, instead of decreasing it. I would think that you would also need checks for if sims are related or best friends or whatever, so that the mod only affects your target sims.

For making a mod like this, it's recommended you start with Echo's Making Your First Custom BHAV Tutorial. There's also this thread: https://modthesims.info/showthread....9&cb=1614716624