Sims not showing up in relationship panel

Product: The Sims 4
Platform:PC
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? 1.108.329 or whichever one was on the 25th of July
What expansions, game packs, and stuff packs do you have installed? All expansion packs except Lovestruck, for rent, High school years, growing together, and Eco Lifestyle. Game: Werewolves, Vampires, RoM, Outdoor retreat. Jungle Adventure, strangerville, parenthood. Stuff:tiny living, moschino, toddler, fitness, backyard, romantic garden, ;uxury party, my first pet Kit: throwback, fashion street, desert luxe, blooming rooms
Steps: How can we find the bug ourselves? I don't know. I don't know what I did. I literally haven't played the game for months, and it was fine when I left it. I play with big families so I'd notice if their relationships were all deleted. Now all my sims have like 5% of their relationships.
What happens when the bug occurs? My sims now only have relationships with their significant other, and any pets and inanimate objects that you can build a relationship with. No friends. No siblings. No parents etc. The only things showing up in the relationship tabs are the 3 initially mentioned. Children with no pets/inanimate friends show as not knowing a single person; not even the people they live with.
What do you expect to see? I have large family trees where everyone knows everyone and their relationship tab should be overflowing with sims. Except they're not.
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. I literally just updated the game

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My sims relationships have been nuked. I've checked various saves with big families to ensure that they weren't just new sims who didn't know anybody. Unless they have a animal, an inanimate befriendable object (talking toilet, stuffed toy) or a partner, there are 0 relationships showing, implying that my sims don't know a single person. For example, I have a sim who has a husband, multiple pets, siblings, parents, cousins etc, and children. The only relationships showing are the relationship with their husband, and their animals. Their children have no known sims outside of the animals.

I tried having a sim talk with her brother, and in the bar at the top it showed 2 bars with no progress in either. Along with that, her brother wasn't re-added to her relationships tab.Despite living with her family, she only knows the pet cat, a rabbit, some birds, and a baby horse.

First file is Morgyn Ember's relationship tab, who in my game has a husband (Javier), 3 children, parents, siblings, friends, and a lot of farm animals. Only Javier and the farm animals appear.

Second file is Morgyn's daughter. She has essentially all of the relations Morgyn has except a partner. None of her siblings show. Her parent, Morgyn does not show either.

Third file is a baby, who apparently knows no one, despite living with her parents and sibling.