Originally Posted by Demise

This does not apply to F-2A category, only to IR. Almost everyone else basically need to maintain continuous lawful status from the day they arrive to the day they file I-485.

Your brother will have to undergo consular processing (i.e. leave, go to consulate abroad, pick up his immigrant visa, and return). You are right however that he has been in a period of authorized stay during his entire adulthood so he won't get a 10 year bar if he departs.