You appear to be stating that he entered the U.S. illegally, and thus the information you have received is correct. He can't adjust his status, as he has no status to adjust. The only way I know for him to gain status would be to leave the country (triggering the ten year period of ineligibility to reenter), then seeking a waiver of his ineligibility. That would be a risk, so it's something he should discuss with an immigration lawyer.

