Hi Kelly,
Traveling to Walt Disney World with a large group can be so much fun! It is great to experience the magic through the eyes of so many different ages. There are many different options for how your party of 12 can stay at Walt Disney World. Let me offer you some choices.
If you all want to stay in one accommodation, you could book a three-bedroom grand villa. These are located at many of
Disney's deluxe villa resorts, and can sleep up to 12 guests. In a grand villa, you will also have a living area, full kitchen, and washer and dryer. These resorts are a part of Disney Vacation Club; however, there are villas set aside for non-members who wish to pay using traditional means such as a credit card.
The other options for your family include splitting up in some way. For some families, this is a nice option because it lets you be with your whole party during the days, and then split up for down time at night. Your party could fit into two cabins at Disney's Fort Wilderness Resort, or into two family suites at Disney's Art of Animation Resort or Disney's All-Star Music Resort. These options all sleep up to six guests each.
Finally, look at
Disney's moderate resort hotels and
Disney's deluxe resort hotels. Many of these have accommodations that sleep up to five guests. Since you and your brother each have families of five, each of those parties could have a room plus your parents could have their own room. In any of these scenarios where you are in separate accommodations, you can request that the rooms be close together. While this cannot be guaranteed; Disney will do their best to honor your request.
Please do let us know if you have any further questions, Kelly!