My boyfriend lives with his sister and brother in law and his brother in law is in the military he is getting stationed in

The age in Louisiana is 17 for what? Who told him his BIL could get in trouble for what? Is it possible for who to stay where? I am having a very hard time understanding what you are asking.

If your boyfriend turns 18 in the week, he doesn't have to go anywhere he doesn't want to. Sounds like your boyfriend wants to go. Not sure why you think of the brother-in-law on the military would "get in trouble", unless he is the legal guardian of your boyfriend.

When your boyfriend turns 18, he is legally an adult (even in Louisiana) - the language is that he will reach the age of majority. As such, he is able to make decisions independently of his guardian (assuming his brother in law is his guardian). That said, it is probably in his best interest to go where he will be financially supported and provided with resources to succeed in life. I am unaware of any provision that states your brother in law would get in trouble with the military unless your boyfriend is under some legal obligation (for instance a term of parole) to remain in his brother in law's care. Perhaps you can provide additional information so we can best assist you within the constraints of this public legal forum.