Connecting rooms at Disney are never a sure fire guarantee regardless of what you are told while booking or even what your confirmation says.
The resort determines who gets them and the only definite is two rooms and "one" adult. More than one adult they can and have seperated other guests before.
If there are 2 adults in your party, and 3 or more children between the ages of 3 and 17, the following resorts
will guarantee connecting rooms.
All Star Movies
All Star Sports
Pop Century
Port Orleans French Quarter
Caribbean Beach
Coronado Springs
Animal Kingdom Lodge
Wilderness Lodge
You must let them know at the time of booking that you need connecting rooms.
There must be connecting rooms available for you. They will let you know if they aren't available.
If in your party of 5, one of the kids is 2 years old or younger, they will not guarantee the connecting rooms, because you would fit into one room at the above mentioned resorts.
If you are a party of 2 adults and 4 children between the ages of 3 and 17, Disney will guarantee connecting rooms at Port Orleans Riverside for you, but the conditions above still apply. (Just like the others if you have 4 kids and one of them is 2 or younger, you won't be guaranteed connecting rooms because you'd fit into one room in Alligator Bayou)
It may happen - but I don't know because I've never encountered it. I would assume if you've got 2 adults and FIVE kids between the ages of 3 and 17, All Star Music would guarantee connecting rooms. That I'm not sure about, but I am sure about the others.