What should I do if the executor is not fulfilling their duty?

My grandmother died in April 2013, my uncle, aunt, brother, and myself are beneficiaries. My uncle and aunt were the executor and executrix. My aunt had a mental breakdown and stepped down from the position. My uncle is involved with criminals, and has shared personal information that was disclosed to only him with criminals, such as social security numbers. He has not shown any progress as to giving anyone their portion of the will, now going on two years after her death. He also cashed in stocks, unbeknownst to anyone and is going through the money sufficiently. He also owes the estate 20,000, but does not have the money. What steps do I take. When the executor is not fulfilling his duties?