I-9 forms asked after interview. Any input?

[Inwood]

My sister (US citizen) married an illegal alien and he is trying to become a permanent resident. Today he had an interview in the Immigration offices, and the interviewer is asking for a copy of I-9 forms of the places where he worked in USA. He has to send this documents in the next 30 days. Since he was illegal when he worked in those companies he might be in trouble if he sends the I-9 forms he filled. The other option is getting a letter from each of the former employers stating that they currently don’t have those forms, since he finish working for them in a certain number of years.

Those anybody has been in a similar situation or has any advice or input on this matter?

Thanks,

Inwood.-