It's definitely GGLs and Prems who get two guests, plus a few oddities relating to "guests of BA" where the Special Services can assist. In the case of the GGL one of them needs to be travelling First. In the case of Prems there are no restrictions (open doors). In the file it's the third block down for Golds, but on first glance the second block is Gold (it's actually BA Gold Guest List).