Heat oven to 350°F. Spray 11x7-inch (2-quart) glass baking dish with cooking spray. Cook pasta as directed on package, adding broccoli for the last 2 minutes of cooking. Drain pasta and broccoli.
In large bowl, mix Alfredo sauce, milk and pepper. Stir in shrimp, crabmeat, parsley and 2 tablespoons of the cheese. Add pasta and broccoli; toss gently to mix well. Spoon into baking dish. Cover baking dish with foil.
Bake 35 to 40 minutes or until hot in center.
Meanwhile, in small bowl, mix remaining 2 tablespoons cheese, the butter and bread crumbs. Sprinkle over casserole. Bake 10 to 15 minutes longer or until top is light golden brown.