[ARCHIVED] Cannot edit pre-existing sims (Family relationships)

Product: The Sims 4
Platform:PS4
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.70
What expansions, game packs, and stuff packs do you have installed? incheon arrivals, my wedding stories, pastel pop kit, country kitchen kit, cottage living, discover university, toddler stuff, spooky stuff, luxury party stuff, spa day, get famous, bowling night stuff, romantic garden stuff, get together, fitness stuff, cats and dogs, cool kitchen stuff, island living, laundry day stuff, dine out, outdoor retreat, movie hangout stuff, kids room stuff, vintage glamour stuff, seasons, get to work, city living
Steps: How can we find the bug ourselves? use the cas.fulleditmode cheat on a household and try to change the relationships of the members.
What happens when the bug occurs? I can't edit the relationships, they're still greyed out and acting as if I haven't downloaded the cheat. options for parents also don't work because of this/don't appear for either sons.
What do you expect to see? I expect to be able to change their relationships while the cheat is enabled.
Have you installed any customization with the game, e.g. Custom Content or Mods?  I'm sorry I don't know what custom content means, but all ive consciously downloaded is the packs and stuff, I don't really understand how mods work in this game, I just started trying to use it for the relationship editing. 
Did this issue appear after a specific patch or change you made to your system?Neutral/Not Sure. 

Hi! so I've been playing a household of two people, I've played them for ages and their relationships are maxed (engaged atm) and both have degrees from university and have peaked in respective careers. since they're engaged, I got the wedding stories pack and decided I wanted to create parents for my sim's fiancé, Leo. Also, I recently created Leo's brother, Miguel (same household), in case that means anything. I successfully used genetics to make Leo/Miguel's parents (using Leo's genetics both times), and each one can be Leo's parent without using any mods. I can also have them be husband and wife. The issue I'm facing is that I can't have them be Leo's parents at the same time. Both his mother and his father can be his parents successfully, its not that only the father works or vice versa, so I dont think this is related to his family tree, which from my understanding can automatically fill a parental role and cause a similar issue? When I created or selected one of the parents' relationships with Leo, i.e. his mother, and selected her as his mother, the father's relationship defaults back to household member. I can then still see the option for his father to be his father again, but when I select that, the mother defaults to household member; this goes on infinitely.

I used the fulleditmode cheat because everywhere I searched said it allows you to edit your relationships for existing sims, but it doesn't work: it greys out the relationship options for Leo, and restricts Miguel's to household member or fiancé when selected by either the father or mother. For Leo, it says the message that I cannot edit an existing sim, which I thought this cheat would bypass. Also, if its important, I get a little yellow !  hazard icon on Leo's portrait (and his relationship thumbnail too) when I create his parents and I can't find out what this means, not sure if its related to the issue!

I've scoured a lot of forums and videos about this issue and no answer is fixing this. I'm absolutely not willing to save Leo to my library and delete him from the household, because he has relationships, skills, maxed career and a university degree that I'm assuming will be erased if I do this. I've also seen people say I need to delete his relationship with Miguel, but I can't find a way to do this on PS4, every suggestion is about a PC modding thing I can't access. I also tried selecting Miguel as a household member to Leo, but even though the option exists and I can click it, it doesn't change and they stay as brothers. I tried to change this in fulleditmode and it didn't work here either as Leo is greyed out again. 

I'd really appreciate any solutions to this. I know I might be wrong/misunderstanding something but it doesn't seem to me like I'm experiencing the same issue as similar threads, because the issue isn't that I cant make a character his parent, but that I can only give him a single parent, either mother or father. If there's no solution I'd also appreciate knowing so I can at least stop trying to solve this! but im baffled at how this could be impossible. Again, I really don't want to have to save him to my library and reinstall him, because I'm not willing to go through his career/university/relationships again! 

Screenshots: the first cap is showing how when I added the dad, Julio, Sofia (mum) defaulted back to household member, she was mother to both Miguel and Leo before and it seemed perfect until Julio was added and replaced her. the second cap is when I went back into CAS using the cheats, and I wasn't able to even touch Leo's relationships to change anything. the last cap is also in the cheats version of CAS, and my only options for Miguel with both parents are fiancé, partner or household member. I actually get less options with the cheats, as I can usually select everything when I genetically make the two parents for the first time, they just dont work at the same time as each other!

Sorry this was so long, please let me know if I need to submit more shots or explain anything better!! <3