You should also find out if anyone ever petitioned him (or his parents when he was under 21 years old). He may be covered under a law commonly known as 245i. See an experienced immigration attorney who can advise you on that. There are other ways to qualify as well such as if he had a previous marriage and a petition was filed for his ex-wife. There are filing dates to meet in order to be qualified but it is worth looking into. If he does not qualify under such as law, he can then consider a consular process but he will require a waiver for his prior unlawful presence.