Possible Portal 2 spoilers ahead, be advised.
I noticed at the Bring your daughter to work part the overgrown potato-science project had Chell's name on it. This confirms that Chell is in fact a daughter of an employee and not a random test subject. This also means that her parents might actually be in the cryo-storage as Glados implies at one point.
The middle panel's bottom right has "by Chell" written on it.
poor chell. she has to deal with GLaDOS and the tests, and has no family to be found. Heyjude333 13:23, April 20, 2011 (UTC)
Also on that project poster is the line "Special ingredient from dads work". This implies she is at least the daughter a male employee, whether her mother works there is unknown. Also could someone add this too her page, Its locked and I can't touch it.
GLaDOS at one point say: I found two persons with same surname as yours. Man and woman. World is small. This can meat that Chell parents are in cryo --Shopingjs 15:42, April 23, 2011 (UTC)
Here are my two cents worth: Chell was abandoned by her parents at birth, and then found and adopted by an employee of Aperture Science. Maybe she never knew that she was adopted and only found out from GLaDOS. Then the BYDTW-day massacre happened and people were stuck there for 20 years, and Chell learned and helped the scientist to do... erm, "scientific" stuff. (for a lack of a better word.)
And when she jumps instead of answering Wheatley she's just being cocky. --Rei. 23:32, April 23, 2011 (UTC)
Glados cant know if Chell's parents are in Aperture. Chell's last name is [REDACTED] not even Glados knows it. Also if one remembers Glados says you will get to meet them then when you get to said area she says surprise and no one is there. glados did not take over on BYDTWd and chell wasnt trapped there for most of her life. http://half-life.wikia.com/index.php?title=Forum:Aperture_Timeline_Retcon_Most_are_Missing&t=20110429102455 . Theres a timeline that I made and it answers all of chell's age problems. SajuukKhar 12:21, April 29, 2011 (UTC)