Good 2D animation software that is free and good for beginners? (don't suggest Pencil or Pivot please)?

I want to pitch this show to Cartoon Network called Brotherly Hate, and the plot is about 2 brothers who hate each other with a passion and are always competing against each other. I have the idea and everything (I even know how to draw them!), but I want to animate it. My Flash trial is up, and Pencil or Pivot haven't given me any luck. Can anybody suggest a good 2d animation software that's free, easy-to-use, and not Pencil or Pivot?