FWIW,
Dreams Unlimited Travel, which I'm sure everyone knows is who is behind Disboards, says that you *can* get guaranteed connecting rooms if it is an immediate family (i.e., parents and their children) and there are more children than adults. I know this has been touched on in this thread, and some have said that even that is not guaranteed. But I'm just telling you what Dreams says.
This exact issue was addressed on an episode of the
Dreams Unlimited Travel podcast. Here is that video. The relevant portion begins at 4:47, which should be where this video starts.