sibling cats mated

Question
I have an 8 month old kitten and my father in law had her brother from the  same litter. We were cat sitting and apparently now my female cat is pregnant.  I didn't realize she would be in heat so early but she appears very pregnant and the only male cat she would have been exposed to is her brother.  Will the cats be deformed?  I've been told by a friend they'll be deformed and i'll have to put them all down. Any help is appreciated.

Answer
There is a possibility there will be defects, but more likely they will be smaller and maybe not as healthy their whole lives.  Inbreeding in animals is a bit more forgiving than that of humans.  You will just have to wait and see when they are born, but I doubt it will be necessary to put them to sleep.  Make sure to get them both spayed and neutered to prevent this in the future.