One of my cats was mis-aged by the shelter as well. I had her first vet's appointment scheduled for Friday (I got her on the weekend) when she went into heat - she was supposed to be only 3 months old). The vet said that since she was probably already preggers (I got her un-neutered bro at the same time), the spay didn't really need to be rushed anymore. When he did the spay, he aborted what he thought were probably 3-4 fetuses.
Similar situation though - he didn't think she'd survive the pregnancy and the kittens might've been off since they were brother and sister parents (we have since come to suspect that THEIR parents may have been brother and sister too although maybe they're just really dumb cats.
Storm (beeps and has a pink nose and toes),
Misty (with big blue eyes and tasseled ears),
Anya (only ever called Honey - she's that sweet),
Zander (who goes by Punkin' cause he's almost that bright)
Kasee (couch potato who thinks she's a dog)