can I fight my brother for ownership of my grandfathers vehicle?

My brother forges my grandfathers signature prior to his death. For many many years it has been stated by my grandfather that should anything happen to him, he would leave me his car. My grandfather raised me into adulthood and the car means so much more then anyone would understand. It was also known to everyone in my family that I would get his car if/when he passed. My aunt is currently the executor of his will and told me that there was nothing specifically noted about his car. she also told me that my brother may or may not have put my grandfathers car into his name. What is my recourse in the matter. I need insight to proceed properly to save my grandfathers car from the scum of the earth.