For the fall of '07 its probably a little late to apply anywhere. Considering the applications are usually pretty intensive and most dates for applications have gone by.
A 3rd engineer...and I thought I would be the only licensed marine engineer around. If he doesn't end up attending in 2007 tell your brother he should upgrade his license if he has the sea time. I graduated in 2002 with my 3rds and most of my friends from school who have shipped out for 5 years now are 1st or chief engineers. If anyone in the admissions office understands the license structure they will see the hire the rating as an indication of more leadership responsibility.
I am sure he has some interesting subject matter to write about in his essays which is good. Plus its a rather unique background and really can look good to admins judging from some of the alumni from my school. I know several who have gone to HBS, GSB, and a few other top schools. A few who I have talked to said that they all made big impressions during interviews with schools and later with companies.
Good Luck.