Twin lakes actually has two campgrounds associated with one name, and they are right next to one another. This twin lakes is older, with a boat ramp and ONE port-a-jon... but this one has almost all shade and canopy, has campsites tucked away from the others, sits right on the North-South trail, and sites 5 & 6  are blended into a bigger group type campsite.  There are no amenities here, and my cell signal was iffy one moment and three bars the next (AT&T). Follow the directions to the Twin Lakes sign, then take the turn by the "boat ramp" sign on the left at the fork. Follow it back a good ways, and it will open to the campground. All sites are first come, first serve, require a Basic Campground (Dispersed) camping permit which you have to purchase at any of the visitor's centers prior to your arrival. 

I believe this campgound was originally intended for those to use while hiking the full (or north leg) of the North-South trail, and as vehicles kept coming back, the "roads" back to the sites off the water developed. I wouldn't bring an RV back here to boon dock, unless you knew you were going to end up on site 5 or 6... and then it would still be a maybe.