Official PROOF that Cave is NOT Chell's father
mr.johnson is the father. chell refers to him as this because she grew up being raised by rattmann because thay put her up for adoption due to the fact that she would interfear with his work. They still wanted to be close to her so they made an aperture employee adopt,... rattmann!
This "proof" doesn't say that Cave isn't Chell's biological father. Rattman has adopted Chell from the Johnson's. Cave made Rattman do this, because it was the only way for Cave not to have parental care for her but still be near her. I made a pastebin about this: http://pastebin.com/Jrjx5Mx3 (I wrote it in norwegian and couldnt be arsed to translate to english, so I used google translate).
it is a good point , but remember, Chell was adopted , Cave still could have been her father but was far too devoted to his work and gave her up for adoption, but he still wanted to keep an eye on his child so he gave her away to an aperture employee.
Cave is probably chells father because chell is addopted and cave probably dosent have time for a child and Caroline is her mother because when glados found out that she was Caroline glados dident have much hatred for chell like in portal 1 or at the begining of portal2
That makes no sense. Chell NEVER refers to Johnson as her father, most likely because she has never spoken a word in the games. And this is just pure speculation. Until Valve releases more information officially, I'm going to stick to Chell's father being an unnamed Aperture employee.
ok, great. now that we have that settled, let's talk about what the name of the city is in mirror's edge. 
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Im blue, a Clean Christian Furry with Autism.
i think chells parents are CaveJohnson and caroline because if you translate the end song in latin with the turrets the answer is there watch it http://www.youtube.com/watch?v=SDotlkKzvnc
i found information regarding the cubes that strongly indicates some disturbing theories, though technically unrelated to this original discussion is still interesting
http://www.youtube.com/watch?annotation ... 5w6ieaTxGA
Actually, what happened is that Caroline is Chell's mother and Cave Johnson is Chell's father, but when Chell was born it turned out that Cave and Caroline couldn't care for her because they were so dedicated to science. So they gave Chell up for adoption and Doug Rattman adopted her. That explains her saying something about "something from Dad's work". They kept her birth parents a secret.
If you'll remember in Portal 2, GLaDOS mentioned the fact that Chell is adopted. And you can tell from the recording in the OLD Aperture Caroline is Cave's wife. Look it up on Portalwiki. He says "Sorry folks, she's married. To science!" Portalwiki says that when he says "To science!" Cave is actually referring to himself. Caroline's devotion to Cave Johnson is the same kind that a woman would have for her husband.
Also, when GLaDOS realizes that she "is" Caroline, she develops a more "motherly" or "loving" personality at the end and lets Chell go.
See this picture? That is apparently when they found that Caroline was pregnant.
http://4.bp.blogspot.com/-vCWGqXKqRrs/T ... nt_low.png
They are looking troubled because they can't care for Chell when they are so busy with science.
Chell's last name is Redacted presumably so no-one can link her to the owners of Aperture.
So, to sum up, Cave and Caroline are Chell's parents and Doug Rattman is Chell's adopted father.
Does that make sense? Because I got this information from a trustworthy source, and all this info is as close to the truth as you can get.
Hang on. I was just watching someone play Portal 2, and GLaDOS said that she foung two people with Chell's last name. A man and woman. It could actually be that the man and woman are Chell's adopted parents and Doug could be someone she doesn't know but who helped her anyway, or he could be her friend. The part concerning Chell's adoptive parents is still a little sketchy so... yeah.
What is this "reliable source" you got the information from? And I don't think that picture is canon, as it isn't in the game.