Thanks everyone for your insight... seems the rules vary from congo to congo from what I'm reading here (even though the GB would probably prefer that everyone follow the elder's manual)...
A little more info just came to light... last night I found out that my nephew actually moved out after a "conversation" with his elder father that went sour very quickly. After my nephew made it clear to his father that he had no intention of ever going back to the kingdom hall, that he will continue to date his non-JW girlfriend and that he is now 18, his father repeatedly suggested to him that it's probably a good idea for my nephew to get his own place as he was concerned that his qualifications might get called into question or his privileges removed. So there wasn't really a forceful push to get him out of the house per say, just your usual WT-style guilt-inducing mental manipulation (which seems to work every time).
However, regardless of what the elder's book says about this scenario or what is put into actual practice, the bottom line here is that, in my brother-in-law's mind, he was basically presented with a choice... a) his son ; b) his privileges
but his JW mentality led him to make the wrong choice, again.... very sickening indeed