My sims disappeared!

My game has decided to delete a ton of families from my neighbourhood. it says they still live there, but the household is totally empty, leaving my only option to delete them. my sim's wife and kid lived separately; they're gone. they don't even show in his relationships. another of my sims had a baby. i moved her and her baby out. go to play them in their new home...baby has disappeared, as has its father (from relationships panel and game). all thats left is the 'new baby' moodlet. this is game-breaking for me. seriously unimpressed.

Do you maybe have a backup ?

Can you check if they still appear in the not placed families (in manage world where you place families)

I had a similar situation happen that I would like to add:

1. I have 4 families living in the neighborhood.
2. I switched from one while they were at work.
3. When I switched back, the sim icons were grayed out as if they were at work even though they were in the house and living. I just couldn't have any part in it.
4. I switched to a different house and instead of taking me to the house, it took me to the park. Again, sim icons were grayed out and I couldn't select them.
5. I fixed the issue by throwing a party and inviting the grayed out sims.
6. I switched families 3 times today.
7. The result being that one family completely disappeared from the neighborhood.
8. That family had family members living in 3 different places and anyone with that last name was removed from the game. The daughter who had gotten married and I manually changed her name was spared.
9. They are gone forever, not even in my library.
10. I did not do it. I went to manage the world so that I could move the last son into his own home when I realized they were gone. Their house still says they live there, but no family pops up. Then the other son who lives in a different house with his wife was also gone.

The biggest part of this whole thing is that anyone with the same last name as the disappearing family was also gone no matter what house they lived in. 

Added

@hgm127 Merged your post in here

• Are you using mods (Please answer with: Yes, Never, Removed) --> It's essential that stuff is tested on vanilla games so remove your mods before reporting a bug.   --- Never.
• Are you using custom content (as in clothing and objects) ? --- No 
• What is your Operating System (XP, Vista, Win 7, Win 8, Win 8.1) ? --- Win 7
• Do you have the download or DVD Version of the game ? --- Download

I'm having an issue where my townie NPC friends are disappearing. Though my Sim clearly establishes a relationship, when I go to call them they aren't on my 'friends' list. At first I thought they might be dying off, but some of these Townies are clearly adults/teens. They don't show up as 'Deceased' they are just gone, as if they never existed.

It's now gotten to the point where its impossible to make/keep friends with any Sim that is considerable 'unplayable' (i.e. a townie). I have to move in random sims  to have a decent gene pool around. It could be /I'm/ missing something or doing something wrong - but I didn't have this issue when I first started my household, it came in later generations (on 3 currently). 

PS I did a search and poked around before posting, didn't see anything simillar on this. But it's also early here and my brain might not be functioning. Apologies if this a repeat. 

I'm not sure if this is related, but a bit of pre-history.
Russian localization is disgusting, and the worst part of it is Russian names for the sims. Considering the system fills the town with random sims, I deleted them all and recreated with the families taken from the library. I've made several families with 8 people and the divided them onto 8 homeless families with some kind of relations between them. However this barely helped, because the game generated 25 more families with stupid names. For now it looks like random townies substitute my own, because there's way more randoms comparing to those townies I made. 
The bad point in this that non-played families nearly no developing, they can just die lonely, so no reproduction - no story. 

Now the bug itself. I've been playing with three families, they had wonderful interrelations, including the Goths. Mortimer died, Bella remained with Cassandra, Cassandra's girlfriend, girlfriend's son, Alexander Goth' wife Emy and her boy as well. Alexander was living separated, as well as Emy's sister and mother. Then his wife had moved to Alexander with their son, and they all had been loaded and looked well. 
I switched to different family then, and when returned to Goth, I was shocked by what I had seen. 
Goth family - only Cassandra's girlfriend and her son. And urn of Mortimer. All the other family members disappeared with no sign. 
Alexander Goth' family totally disappeared. Empty household with money remained.
Emy's sister and mother also totally disappeared.
I guess some of homeless families I created dissolved the same way, but don't really miss anyone of them as they are not for playing. 
No memories. No relations as if they died or moved. Nothing. 

Ok, I had hard time to recreate them all, get them grow to the stage they were on to build them into the story. 
After moved in with Alexander, Emy and their son had disappeared again. At least Alexander remained this time, and he also had no thoughts of what he had been married with a schoolboy son. 

That is definitely frustrating. I switched to different family. Grew up a girl especially to seduce Malcolm Landgraab and get his house and money. Ok, they at last got to live together. They even had a daughter. And everything was just fine. Until I quit the game. On my return neither daughter, nor Malcolm appeared. And again - no traces they ever existed. Hey, they SHOULD have been there, these are the Goths and the Landgraabs! How it turned to clear out primary sims of the plot?

Originaly posted here - http://forums.thesims.com/en_US/discussion/781004/sims-disappearing#latest

I also had this happen... 

I had a family that was just a guy but I imported a female sim off the gallery and they had two sons together. I went off and played another family and came back to that family when I clicked on their house and noticed it was only the man and his two sons in the description... the mother is completely gone. I checked in the relationship panel for each of them and shes not there either, not even as a grayed out picture and deceased. 

No, they do not appear in any families stored in the library, only those copies of them specially stored at the creation. 

Merged

I started with one family which I split up twice so the members live in 3 different houses. From the initial house, 1 sim has disappeared. From the second house the entire household has disappeared. The third house is fine, which is the most recent one played.
By disappeared I mean in the first house the missing sim's icon is gone, and he is unplayable. In the second house the whole family's icons are gone, but you can still see the household name and funds. When I try to play them the game attempts to zoom into the household but just freezes on the map view. When other sims visit the second house it says "nobody is home".

It's super annoying because the family in the third house have lost brothers, cousins and nieces. The majority of their family has disappeared off the face of the earth.