Question about "walk-though" bedrooms

We have an old house. One of the bedrooms is in the back of the house. You have to walk through another bedroom to get to the back room. Currently, my 16 (bio) son is in that room. We use the walk-through room as his TV room. Lil J is our foster son, and currently shares a very large room with our 2 (bio) girls. But, he will turn 5 in Feb. And, therefore he can not stay in the same room as the girls. I know we can not use the walk-through room for Lil J, since it is a lack of privacy. And, we have been told this - they will not even measure this room. BUT???? Can we use the back room for him? And, then put the girls in the walk-though room? There would not be a lack of privacy for Lil J, as the bedroom has a real door. If anyone has a lack of privacy, it would be the girls. Rights should be terminated in April. So - we would have to do something since he won't be legally ours. I know in the "laws" it says something like "room can not be used for any other purpose" Thoughts? We would have 2 other options. 1 - Keep Lil J in his current room, and put the girls in the walk though. But, that would mean that the 16 has to walk through their room (and possible wake them up) 2 - Put Lil J in the office (which can be considered a bedroom - it has a window, a door, a closet) but it is SMALL. It is only 63 sq feet, which is big enough according to DYFS. Option #2, is a teeny room. Just enough for a twin bed